The subject in which the student scored 180 marks is

method 1:

total marks = 720

720 marks = 360 degrees

1 mark = $$\frac{1}{2}$$ degrees

180 marks = 90 degrees

so the answer is option A.

method 2:

The marks scored in Mathematics = $$\frac{90}{360}\times720$$ = 180

The marks scored in English = $$\frac{60}{360}\times720$$ = 120

The marks scored in Bengali = $$\frac{70}{360}\times720$$ = 140

The marks scored in History = $$\frac{65}{360}\times720$$ = 130

The marks scored in Science = $$\frac{75}{360}\times720$$ = 150

so the answer is option A.