When may you drive in the left lane of a highway with two or more lanes traveling in the same direction?

Answer: D — When passing slower vehicles

You should only drive in the left lane when passing slower vehicles. The left lane is typically reserved for passing and can be highly dangerous when used for other purposes. Option A is incorrect because you should always use the right lane when the left lane is blocked. Option B is incorrect because it is unsafe to use the left lane unless you are actively passing another vehicle. Option C is incorrect because driving in the left lane has specific limitations and should not be done "whenever you please."