A word series is given: tub, size, latin, formal. Choose the option that correctly completes the pattern.

Introduction / Context:
In this verbal reasoning question you are given a series of four English words followed by a blank. Your task is to identify the underlying pattern that links the given words and then select the next word in the sequence from the alternatives. Such questions test observational skills rather than vocabulary knowledge. The key is to look for patterns based on number of letters, positions of letters, or some other simple property. In this case, the meaning of the words is not as important as the structure of the words themselves. Once we identify the pattern correctly, the missing term can be chosen confidently from the options provided.

Given Data / Assumptions:
The following information is provided in the question:
tub, size, latin, formal, ?
Options are: smooth, idle, scramble, capital.
We assume that the pattern is consistent across all given terms and that exactly one option extends the pattern correctly. We also assume standard English spellings and normal dictionary forms of the words.

Concept / Approach:
For word series questions, one of the simplest approaches is to check the number of letters in each word. Many exam questions deliberately avoid deeper or obscure patterns, and instead use a clean numerical pattern hidden in the word lengths. Other possible patterns, like alphabetical order of first letters or last letters, can be checked quickly, but if they do not fit neatly, then the length pattern is usually the most reliable. Here, we will examine the length of each word in the series and then see which option continues that pattern in a natural and logical way.

Step-by-Step Solution:
Step 1: Count the number of letters in each given word. tub has 3 letters. size has 4 letters. latin has 5 letters. formal has 6 letters. Step 2: Observe the pattern in the word lengths. The number of letters forms a simple increasing sequence: 3, 4, 5, 6. Step 3: Predict the length of the next word. Following this pattern, the next word should have 7 letters. Step 4: Check the length of each option. smooth has 6 letters. idle has 4 letters. scramble has 8 letters. capital has 7 letters. Step 5: Identify the option that matches the required length of 7 letters. Only the word capital has exactly 7 letters. Therefore, capital is the correct word to complete the series.

Verification / Alternative check:
To verify the answer, we can double check for any other potential patterns, such as alphabetical order, vowel patterns, or consonant patterns. When we examine the first letters t, s, l, f, there is no clear alphabetical or reverse alphabetical sequence. Similarly, last letters b, e, n, l do not follow a simple scheme. There is also no clear connection in meaning. Because the length pattern 3, 4, 5, 6 is perfectly regular and the next length 7 is uniquely matched by capital among the options, the answer is strongly confirmed. This redundancy check ensures that we did not miss a more complex rule and that the chosen word genuinely continues the sequence in a unique way.

Why Other Options Are Wrong:
smooth has only 6 letters, so it does not move the sequence forward beyond formal which already has 6 letters.
idle has 4 letters, which breaks the increasing pattern and jumps backwards to the length of size.
scramble has 8 letters, which skips directly from 6 letters to 8 letters and does not follow the step by step increase by one letter at each stage.
Thus these three options fail to maintain the simple and consistent length progression that is clearly present in the original series.

Common Pitfalls:
A common mistake in such questions is to overthink and search for complex relationships based on meaning or obscure linguistic rules. Another frequent error is to ignore simple numerical or structural patterns in the words. Some candidates may also get distracted by the emotional or visual associations of the words rather than focusing on measurable features. In exam conditions, it is wise to quickly test easy checks such as length, starting letters, and alphabetical order before considering more abstract ideas. This saves time and prevents confusion. Carefully counting letters and confirming the pattern avoids careless errors.

Final Answer:
The pattern is based on the increasing number of letters in each word: 3, 4, 5, 6, so the next word must contain 7 letters. Only capital has 7 letters, so it correctly completes the series.