Here is the completed table with the correct forms of the verb "to be" in affirmative and negative sentences:
| Affirmative | Negative | ||
|---|---|---|---|
| a) | I am | doing homework. | I'm not |
| You are | doing homework. | You (d) aren't | |
| b) | He/She/It is | doing homework. | He/She/It (e) isn't |
| We are | doing homework. | We (f) aren't | |
| c) | They are | doing homework. | They aren't |