The answer is:
The animals scrambled to get into the barn as the lightning struck.
In the chosen sentence, both verbs in the different clauses are consistent ad accurate because they are written in the Past Simple tense.
The rest of the options are incorrect because the tense of the verbs is not related to each other: they wrongly combine past and present, and present and future tenses.
The right version of them are the following:
Alexander finished his math test and walked to Mr. Smith's desk.
Sampson and Raina watch the fireworks and comment on how beautiful they are.
The police officer rounded the corner and pumped his arms harder.