答:at a time相當於once 或each time 或every time.注意區別以下短語: at one time (曾經) at times(時常)。如I can eat four apples at a time(我一次可以吃四個蘋果),從這句可以看出使用at a time表示每次幾個時前面要有次數意思才完整,如一次一個:one at a time或one by one.