When we were having dinner, the lights went out.

• Correction: Replace "(D) were going out" with "went out" because it describes a sudden event that happened during the action of "having dinner." The past simple tense "went out" is more appropriate here.

30. Getting plenty of rest is really important.

• Correction: Replace "(A) Get" with "Getting" because the subject of the sentence should be a gerund ("Getting") to function as a noun.

So, the corrected sentences are:

1. When we were having dinner, the lights went out.
2. Getting plenty of rest is really important.