a.m.和p.m.是缩写词，有关标点的用法如下：

出现在句尾时，如果句尾是句点（句号），则句点（句号）可省略，但a.m.和p.m.本身后面的点需保留，如（1）。如果句尾是问号，则不可省略a.m.和p.m.后面的点以及问号。

出现在句中，或者后面接逗号、破折号、冒号时，a.m.和p.m.的点不可省略，如（2）（3）（4）。

（1）Yorktown Daily is slowing updates as the storm moves through Virginia, effectively stopping regular updates at 10 p.m.

（2） We will be back reporting at 7 a.m. tomorrow.

（3） Voting sites across the county will be open from 7 a.m. to 7 p.m. Tuesday in the Republican and Democratic party primaries.

（4）The access ramps from Telegraph Road southbound and northbound to the Inner Loop (I-95/495 South) will be closed during daytime hours for roadway construction from Monday, May 9 through Thursday, May 12 from 9:30 a.m. – 3:30 p.m., and on Friday, May 13 from 9:30 a.m. – noon. 

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