A-A+
Most anti-virus programs are scheduled to perf
问题详情
Most anti-virus programs are scheduled to perform. a background check_____ throughout the day on a set schedule.
A．periodically
B．periodic
C．periodical
D．period
参考答案
正确答案：A
解析：在一个完整的句子之后修饰句中某一动词的词语，必须是副词。因此本题选择periodically。
