用N_A表示阿伏加德罗常数的值，下列说法中正确的是[ ]

A、1 mol N₂所含有的原子数为N_A

B、标准状况下，22.4 L水中含有的水分子数为N_A

C、标准状况下，22.4 L氯化氢所含的原子数为N_A

D、24 g O₂分子和24 g O₃分子所含的氧原子数目相等

I'm impressed with his persistence. When he had a problem to solve, he________work at it until he

found an answer. [ ]

A. would  

B. might  

C. must  

D. should