李敏是财会专业毕业的大学生，已取得会计从业资格证书且已从事会计工作二年，因工作需要，他所在单位可以任命他担任会计机构负责人。()

A. It tastes better.
B. It is easier to grow.
C. It may be sold at a higher price.
D. It can better survive extreme weathers.

Ask their professors for help.
B. Look at school bulletin boards.
C. Visit the school careers service.
D. Go through campus newspapers.

A. 脉冲数量
B. 脉冲频率
C. 电压
D. 脉冲占空比