Improve the following sentence by choosing the correct verb form: The teacher as well as his wife _____ invited.

Introduction / Context:
This sentence improvement question tests your understanding of subject verb agreement when compound phrases are joined by expressions such as as well as. The subject phrase the teacher as well as his wife may look plural, but English grammar follows a special rule here. You must choose the verb form that correctly agrees with the true grammatical subject of the sentence, not simply with the nearest noun.

Given Data / Assumptions:
- Sentence: The teacher as well as his wife _____ invited.
- The options offer different verb forms in the passive voice: was invited, were invited, were also invited, was being invited, and No improvement.
- The phrase as well as joins two noun phrases but does not create a compound plural subject in standard grammar rules.

Concept / Approach:
When two nouns are joined by as well as, along with, together with, or similar expressions, the verb usually agrees with the first noun, which is considered the main subject. In this sentence, the main subject is the teacher. The phrase as well as his wife adds extra information but does not affect the number of the subject. Since the teacher is singular, the verb should also be singular. In the passive past form, the correct singular verb is was invited. Therefore, the correct sentence is The teacher as well as his wife was invited.

Step-by-Step Solution:
Step 1: Identify the main subject before the as well as phrase. Here, it is the teacher.
Step 2: Recognise that as well as introduces an additional phrase that does not change the number of the grammatical subject.
Step 3: Decide that the subject is singular, so the verb must be singular.
Step 4: Choose was invited as the singular passive form and read the full sentence: The teacher as well as his wife was invited.

Verification / Alternative check:
Compare the sentence with both was invited and were invited. The teacher as well as his wife was invited sounds formal and correct according to standard rules. The form were invited is common in casual speech but is treated as incorrect in competitive exam grammar. Also, the continuous form was being invited changes the meaning into an ongoing action which is not implied in the original context, where a simple past passive is enough. Hence, was invited is the best and most exam appropriate choice.

Why Other Options Are Wrong:
- were invited: treats the subject as plural, ignoring the rule that the verb must agree with the first noun before as well as.
- were also invited: adds also without necessity and still keeps the incorrect plural verb were.
- was being invited: changes the aspect of the verb and suggests an action in progress, which does not match the simple idea of an invitation having been given.
- No improvement: wrong because the sentence requires a properly chosen verb; leaving the blank empty or with an incorrect form would not be acceptable.

Common Pitfalls:
Many learners look at the nearest noun his wife and switch to a plural verb by instinct. This mistake is especially common in long subjects where extra phrases come in between the main subject and the verb. In exam practice, it is important to strip away additional phrases such as as well as his wife and focus on the core subject the teacher before choosing the verb form. This habit significantly reduces subject verb agreement errors.

Final Answer:
The correct improvement is: The teacher as well as his wife was invited.