11. ______ your teacher ______ (explain) the lesson now? - Yes, ______.

Explanation:

The phrase 'now' indicates an action in progress, requiring the present continuous tense. The sentence is a question, and the answer is affirmative.

Solution:

In the present continuous, questions start with the auxiliary verb 'to be', followed by the subject and the main verb with '-ing'. The affirmative answer uses the same structure.

1. Question: Subject 'your teacher' (third person singular) requires 'Is'. Verb 'explain' becomes 'explaining'.
2. Answer: Subject 'your teacher' (he/she) requires 'is'.

Answer: Is, explaining, is