Answer:
C. -400-/300-/---900-----
Explanation:
You have two restriction enzymes (let's call them A and B) capable of cutting double stranded DNA.
The full DNA fragment is 1600 bp long:
After digestion with enzyme A, you get two fragments of 400 and 1200 bp.
The most probable location of a single restriction site for enzyme A is:
After digestion with enzyme B, you get two fragments of 700 and 900 bp.
The most probable location of a single restriction site for enzyme B is:
Digestion with both restriction enzymes yields three fragments of 300, 400 and 900 bp: