Classic "C trap." If you mistakenly consider conditions #1 and #2 together, then of course they will work, because condition #2 works by itself.
The trick is having the discipline to never arrive at that step. On DS, if condition #2 is sufficient by itself, and condition #1 is insufficient by itself, then you are done: the answer is
Choice B.
Also, if you have a hard time understanding condition #1, then you can use the alternative BD / ACE method instead of the classic AD / BCE method, which allows you to start with condition #2 instead of condition #1.
This "backwards" method makes it clear—if you understand that condition #2 is sufficient—that the answer here must be either Choice B or Choice D.
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My name is Brian McElroy, founder of McElroy Tutoring (http://www.mcelroytutoring.com). I'm a 42 year-old Providence, RI native, and I live with my wife, our three daughters, and our two dogs in beautiful Colorado Springs, Colorado. Ever since graduating from Harvard with honors in the spring of 2002, I’ve worked as a private tutor, essay editor, author, and admissions consultant.
I’ve taken the real GMAT 6 times—including the GMAT online—and have scored in the 700s each time, with personal bests of 770/800 composite, Quant 50/51, Verbal 48/51, IR 8 (2 times) and AWA 6 (4 times), with 3 consecutive 99% scores on Verbal. More importantly, however, I’ve coached hundreds of aspiring MBA students to significantly better GMAT scores over the last two decades, including scores as high as 720 (94%), 740 (97%), 760 (99%), 770, 780, and even the elusive perfect 800, with an average score improvement of over 120 points.
I've also scored a verified perfect 340 on the GRE, and 179 (99%) on the LSAT.