Answer: Cytosine, Thymine, Cytosine, Guanine (option A)
Step-by-step explanation:
In DNA strands, you must use base-pairing rules to complete strands.
The base-pairing rules are:
Adenine (A) bonds with Thymine (T)
Guanine (G) bonds with Cytosine (C)
By using these rules, you can pair the sequence GAGC with CTCG
The sequence CTCG is also represented as the bases Cytosine, Thymine, Cytosine, and Guanine, making A the correct answer.
I hope this helps!