Find the mistakes and correct them

Here are the corrections for the sentences:

29. When we (A) were (B) having dinner, (C) the lights (D) went out.
Correction: Change "were going out" to "went out."

30. (A) Getting plenty (B) of rest (C) is really (D) important.
Correction: Change "Get" to "Getting."

So the corrected sentences are:
29. When we were having dinner, the lights went out.
30. Getting plenty of rest is really important.