Start with one tiny piece of this ugly-looking question. The first set of parentheses starts with a term containing jk2. Check in the second set of parentheses for the same combination of variables and exponents. The first term there matches, so the first step to take is 5jk2−jk2=4jk2. There are no other terms with jk2, so the correct answer must contain 4jk2. Eliminate (C) and (D).
Now you have a fifty-fifty chance of getting it right, so you can guess and go, or you can do one more step to determine if the answer is (A) or (B). The difference between the two answers is the −4j2k term, so focus on the terms in the expression that contain j2k. In the first set of parentheses, you have −2j2k, and then you subtract the 2j2k term in the second set of parentheses. −2j2k−2j2k=− 4j2k, so the correct answer is (B).