Let's dissect each sentence to see which one makes the most sense here...
Me gustan mucho las tortas de chocolate porque es muy amargo. This sentence is not grammatically correct because "las tortas" is plural and "es" is singular. It is essentially saying "I like chocolate cakes because they is very bitter" which we know is incorrect. Next option.
Me gustan mucho las tortas de chocolate porque son muy deliciosas. This sentence is completely correct - if you notice, "es" is replaced with "son" - the correct plural form for "las tortas". This will remain a viable option.
No me gustan mucho las tortas de chocolate porque son muy deliciosas. This sentence is not as feasible because it translates to "I do not really like chocolate cakes because they are delicious." You can safely eliminate that one.
Quiero comer las tortas de chocolate porque mi abuelita le gustan mucho. The question regards the speaker's taste in food, not his or her grandmother's; his grandmother's taste is irrelevant. Next option.
Me gustan mucho los deportes porque son deliciosas. This sentence is grammatically correct, but makes absolutely no sense ("I really like sports because they are delicious" - what?). Eliminate this option due to its absurdity.
Answer: B. Me gustan mucho las tortas de chocolate porque son muy deliciosas.
