Which cell structure is mainly responsible for
releasing energy from food molecules in some
single-celled organisms

the answer is d

explanation:

dan realized that his goal of going to an ivy league school if only he works hard which means basically this   to become completely aware of (something) as a fact; understand without a doubt to make (something desired or anticipated) occur to give real, definite or physical form to a plan, dream, or goal to earn (money or a profit) from a deal

b mirrors submit a iisner? e. for which optical devices does d sometimes have a positive value? o a a and b o b. a and c o c. b and d 0 d. b and cb