Here's why:

* DNA Base Pairing: In DNA, bases pair up in a specific way:

* Adenine (A) pairs with Thymine (T)

* Guanine (G) pairs with Cytosine (C)

* Opposite Strand: When you have one strand of DNA, the other strand is complementary. This means the bases in the opposite strand pair with the bases in the original strand.

* Your Example:

* a pairs with t

* t pairs with a

* c pairs with g

* t pairs with a

* c pairs with g

* g pairs with c

Therefore, the opposite strand is tagagc.