Use a question mark to end an interrogative sentence.
Have past efforts to develop an AIDS vaccine been based on the wrong approach?
Use a question mark to change a declarative or imperative sentence into a question.
Their testing of the system was exhaustive?[declarative changed to interrogative]
Start production on Friday?
[imperative changed to interrogative]
When a directive or a command is phrased as a question, a question mark is optional.
Will you please send me a progress report by June 10?
Will you speak to the vendor about the networking
Use a question mark to indicate uncertainty about data.
The first synthesis was accomplished by Claude Poux (1810?-1897).
Do not use a question mark at the end of an indirect question.
James asked whether increasing the bandwidth of the network's backbone would significantly increase performance.