Committee member W wants to schedule a one-hour meeting on Thursday for himself and three other committee members, X, Y, and Z. Is there a one-hour period on Thursday that is open for all four members?

We want to find a one-hour period on Thursday that is open for all four members. The question stem doesn't tell us anything about any of the member's availability. This means we need to know at least some information about the availability of W, X, Y and Z to solve.

Statement 1 doesn't tell us anything about Y or Z. Insufficient.
Statement 2 doesn't tell us anything about W or X. Insufficient.
Together, we know some information about all four members' schedules. Is there a time when all of the schedules overlap?
W and X are free from 9am to noon. Y is free from 10am to 1pm. So there's an overlap for W, X, and Y from 10am to noon. Z is free from 8am to 11am. So there's an overlap for W, X, Y, and Z from 10am to 11am. This gives them one hour where all four are available for their meeting. Sufficient.