In which sentence is the underlined verb in subjunctive mood? if david were walking quickly, he might be on time. david does walk quickly to ensure that he is on time. david walks quickly all the time. david, walk quickly and be on time?

The sentence in which the underlined verb is in subjunctive mood is: if david were walking quickly, he might be on time. The subjunctive mood is needed to state about either conditional or imaginary situations. This sentence is a bit similar to the meaning of second conditional because it expresses a supposition or something hypothetical so it is suitable because it follows the main usages of subjunctive mood. 

Joke: i thought it said drake and josh at first answer: probably unsure about this law. depending on how long the time is.