The correct answer is C. for.
The word “for” is used to indicate a period of time during which something happens. In this case, the sentence is saying that all men between the ages of 18 and 25 are expected to serve in the military for a certain period of time.
The other options are not as appropriate in this context. The word “with” is used to indicate that something is happening together with something else. The word “without” is used to indicate that something is happening without something else. The word “during” is used to indicate that something is happening during a particular period of time.
In this case, the sentence is not saying that all men between the ages of 18 and 25 are expected to serve in the military together with something else. It is also not saying that they are expected to serve in the military without something else. It is simply saying that they are expected to serve in the military for a certain period of time. Therefore, the word “for” is the most appropriate option.