题目内容

当T0x12设置为1，TMOD设置为02H，系统时钟频率为12MHz，IAP15W4K58S4单片机定时/计数器T0最大可定时的时间为256us.

A. 对
B. 错

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Task 2 Using the wordsChoose the proper word or phrase in the box to fill in the blank in each of the following sentences. Change the form where necessary.consumeappetitestick tocuriositysuffer fromdue tocountlessadaptation1. Each year Americans a high percentage of the world's energy.2. She the gossip of her neighbors.3. The television station apologized for the interference, which was bad weather conditions.4. The cat felt when she saw her own reflection in the mirror.5. See how many plates we have, but don't in the cracked ones.6. may need to be made in branding, labeling and packaging of the product.7. If you to the truth, you've nothing to fear.8. Why don't you go for a walk? It'll give you an for your lunch.

主键，（）KEY，用于唯一标识某条记录，作为主键的值必须唯一，且不能为（），主键可以是单一字段，也可以是多个字段的组合，每个数据表最多能有（）个主键约束

DEFAULT约束叫做（）约束，若某属性字段设置了default约束，系统会自动将该值插入。

unique约束，（）约束，指的是记录中字段的值不能重复出现，要求表里某个字段的值在每条记录里都是唯一的。