In this English grammar sentence improvement question, you are given the sentence: The proposal was full of if and but that I seriously doubted whether the stadium would ever be built. The underlined phrase if and but is awkward and does not follow the normal idiomatic expression. Choose the option that best improves the underlined part while keeping the original meaning of the sentence intact and select No improvement only if no change is required.

Introduction / Context:
This question tests knowledge of idiomatic English and correct pluralisation when we name words as objects. The sentence talks about a proposal that is full of conditions and objections, and the underlined expression uses the common idiom that refers to many doubts and excuses. Examinations in English usage often check whether learners know the correct form of fixed expressions like this one, because they are very common in spoken and written language and are important for natural sounding communication.

Given Data / Assumptions:

• The original sentence is about a proposal that contains many conditions and reservations.
• The underlined phrase is if and but.
• The answer choices offer different plural forms of the words if and but, plus a No improvement option.
• The task is to choose the most idiomatic and grammatically acceptable improvement.

Concept / Approach:
When we talk about words themselves, we treat them as countable nouns. In English, we normally form plurals of simple nouns by adding s at the end, so if becomes ifs and but becomes buts. The idiom full of ifs and buts is a set expression that means full of doubts, reservations, and objections. Native speakers recognise this fixed phrase, so any other spelling or form sounds incorrect or at least non standard. The approach is therefore to identify which option reproduces the recognised idiom correctly and keeps both words in the plural form to show that there are many conditions and objections in the proposal.

Step-by-Step Solution:
First, read the entire sentence and understand that it describes a proposal that contains many conditions and reservations. Second, focus on the underlined phrase if and but and notice that it is referring to the words themselves rather than to their normal conjunction use. Third, recall that the accepted idiom in English is full of ifs and buts when we speak about many excuses or objections. Fourth, evaluate each option to see which one matches this idiomatic form without adding unnecessary letters or using a singular where a plural is needed. Finally, select the option that uses ifs and buts in the standard plural form, which correctly expresses the idea of many conditions and objections.

Verification / Alternative check:
A useful check is to imagine how native speakers commonly say this in real life. People normally say There were too many ifs and buts in his explanation or I do not want any ifs and buts about this decision. In each case the plural forms ifs and buts are used. You can also consult a good learner dictionary or corpus and search for the phrase full of ifs and buts, which will confirm that this is the standard idiomatic expression. Options that use mixed number, such as a singular but, or that use altered forms like butts, do not appear in standard references for this idiom.

Why Other Options Are Wrong:
Option A uses ifs and but, which mixes a plural with a singular form and therefore does not correctly show that both kinds of conditions and objections are many in number.
Option B uses ifs and butts, but the word butts normally refers to things like cigarette ends or the backs of animals and has a completely different meaning from the conjunction but, so it is not suitable here.
Option D suggests No improvement, but the original phrase if and but is not the fixed idiom and sounds unnatural, so it should be improved.

Common Pitfalls:
Learners sometimes think that words like if and but cannot take normal plural forms, or they may feel that adding s looks strange. Another common mistake is to write the idiom with an apostrophe, such as if's and but's, which is not standard in modern English. Some candidates may also be distracted by humorous or near homophone options like butts, which can look plausible at first sight but change the meaning completely. It is important to remember that when we talk about words themselves as items, we normally treat them just like regular countable nouns and apply normal plural rules.

Final Answer:
The correct improvement uses the standard idiomatic expression that describes a proposal full of conditions and objections, so the best choice is "ifs" and "buts".