English Grammar
Hi friends which tense I should use for the word "realize" when the phrase "at that moment" is in the sentence.

A.) when you did not answer my call, I realized that something bad happened at that moment.
B.) when you did not answer my call, I realize that something bad happened at that moment.

Question

English Grammar
Hi friends which tense I should use for the word "realize" when the phrase "at that moment" is in the sentence.

A.) when you did not answer my call, I realized that something bad happened at that moment.
B.) when you did not answer my call, I realize that something bad happened at that moment.

Answer

"Reallise" relates to 'did not call'. Because you start the sentence in the past tense, and you are talking about the same frame of time, you continue with the past tense, 'realised', but you would rephrase it:
'When you did not call, I realised that something must have happened at the very moment when you were supposed to have called.'