Which represents a deletion of the section of dna shown here? a—c—t—g—g—a—t a. a—c—t—g—g b. a—g—c—t—g—g—t c. a—c—t—t—g—a—t d. a—c—g—g—c—t—t

The easiest way to tell is to line them all up in a column.

A - C - T - G - G - A - T
A - C - T - G - G
A - G - C - T - G - G - T
A - C - T - T - G - A - T
A - C - G - G - C - T - T

The shortest one will be a deletion. This is answer A. The last two letters in the sequence (A and T) have been removed.