What would be the complementary sequence to GATAACA?

Answer: Option A

The complementary sequence to GATAACA is TGTTATC.
In nature complementarity is the base principle of DNA replication and transcription as it is a property shared between two DNA or RNA sequences, such that when they are aligned antiparallel to each other, the nucleotide bases at each position in the sequences will be complimentary.
The double strands of DNA complement each other. Base T pairs with A and G pairs with C, thus the sequence complementary to GATAACA will be TGTTATC.