period
The mark that ends a statement, a mild command, or an indirect question.
A period ends a sentence that makes a statement: The meeting starts at noon. It also ends a command given without strong emotion: Close the door when you leave. A sentence that reports a question rather than asking one also ends with a period, because the sentence as a whole is a statement: She asked whether the store was open.
Examples
UseThe meeting starts at noon. (The sentence makes a statement, so it ends with a period.)
UseClose the door when you leave. (The command carries no strong emotion, so it takes a period rather than an exclamation point.)
UseShe asked whether the store was open. (The sentence reports the question rather than asking it, so it ends with a period.)
AvoidShe asked whether the store was open? (The sentence reports the question but does not ask it, so a question mark does not belong at the end.)