$\frac{2}{3}$ ＋ $\frac{1}{3}$ ＋ $\frac{5}{7}$ ____ $1\frac{1}{18}$             $\frac{5}{6}$ ＋ $\frac{5}{8}$ ＋ $\frac{3}{4}$ ____3

$\frac{7}{8}$ －（ $\frac{1}{3}$ ＋ $\frac{1}{2}$ ）____0           1＋ $\frac{1}{2}$ － $\frac{1}{3}$ ____ $\frac{1}{6}$

$\frac{9}{10}$ － $\frac{2}{3}$ ＋ $\frac{1}{10}$ ____1

下列有关生物体结构层次的说法，正确的是（   ）

    What about my plans for the summer vacation? First, I will go to Shanghai with my sister Kate. There are many interesting places in Shanghai, and we can also taste the delicious food there. After that, I will spend some time reading books. I will play tennis with my friends, too.—— Peter

    I made some plans for my summer vacation. First, I will help more at home. My parents are always busy, so I'll help them with the housework and let them have more time to relax. Second, I will practice the violin every day. Third, I think the vacation is a good time for me to do some sports, such as running and swimming. I am sure my summer vacation will be wonderful.——Tom

    After about four months' study, the summer vacation is coming. Here are my plans. First, I will leave enough time for my new lessons. I will also read some great books. Second, I will go to Xi'an and stay there for two weeks. I think the trip will be wonderful. Then, I will come back and enjoy myself with my friends. We will go swimming, shopping, etc.——Amy