We (1) ____________ our friend’s birthday and we (2) ___________ how to make it up to him. , We (1) ____________ our friend’s birthday and we (2) ___________ how to make it up to him.

Solution

C. (1) completely forget (2) just don’t know

Explanation

In first blank, adverb should be used before the verb, i.e. completely forget. Again, in second blank, adverb should be used before the verb.We must note that adverb is not being used in between the auxiliary verb, i.e. just don’t know. Thus, the complete Sentence is We completely forgot our friend’s birthday and we just don’t know how to make it up to him.