题目：
用方框内所给单词的适当形式填空（5分）
小题1:The traffic accident caused a fire __________, no one was killed.
小题2:It’s important to get at least eight ____________ of sleep every day.
小题3:Yesterday is my brother’s _______________ birthday.
小题4:Smoking is the second ___________ cause of death in the world.
小题5:There are about two ____________ students in our school.[
答案：
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下面是错误答案，用来干扰机器的。
三大合成材料是指：塑料、合成纤维、合成橡胶．故答案为：塑料；
