语法填空

    ____ is well known, optimism(乐观)plays an important role in one's life. Although we are facing many difficulties, we should keep optimistic. Optimism is a mental(精神的)attitude or world view and it means expecting ____ best possible result from any given situation.

    I did ____ (poor) in English in the past, but I never gave up struggling(搏斗). All my families, teachers and friends encouraged ____ (I) and they taught me a lot of ____ (use) ways of learning English. I ____ (keep) practicing as they told me to do. I listened to English news and songs and I read interesting English stories. At weekends, watching some English movies was another good way to make my English better. ____difficulties I came across, I tried my best to work them out. I believe in myself, ____ (believe) that hard work would finally pay off. Gradually, I make progress in my English. Nowadays, I can remember English words ____ (easy) and use them freely when communicating with foreigners.

    Thanks to optimism, I have become one of the top English ____ (learn) in my school now.

在有理数（-1）²、−(−$\frac{3}{2}$)、-|-2|、（-2）³中负数有（　　）个．

1. 苹果的质量占所有水果总质量的$\frac{2}{5}$，是把（）看作单位“1”。

已知：X（g）+Y（g）⇌3Z（g），X与Y在有催化剂的条件下发生反应建立平衡（如图中实线所示），在无催化剂的条件下发生反应建立平衡（如图中虚线所示）．则相应的图示中正确的是（　　）