清朝乾隆年间，官员刘方霭在奏折中提到了农民“无田可耕，则力佃人田；无资充佃，则力佣自活”的现象，这种现象反映了（    ）

根据短文内容，用方框中所给的单词的正确形式填空，使短文通顺、完整。

    In1997, Bobbi McCaughey gave birth to seven babies. They all survived(存活). This autumn, McCaughey's children are preparing to have ____18th birthday.

    Eighteen years ago, the birth of McCaughey's seven children was huge news across the world. Bill Clinton, American President at that time,____ the family and congratulated them. Doctors worried that they wouldn't survive their first few days, but they did. Many people helped them and they grew up____.

   "Somany things have happened in 18 years. All the happiness and ____are special to us,"said Mum Bobbi McCaughey. Now her children are____to graduate from high school.

电动机通电时转子转动，电能转化成 ____能。交流电动机也是靠着通电导体在磁场中 ____来运转的。电动机具有 ____、 ____、 ____、 ____、 ____的优点，广泛的应用在日常生活和各种产业中。

制作动物细胞临时装片时，要先在载玻片上滴一滴生理盐水，主要是为了（  ）