The president of the United States appoints the cabinet members, _________ appointments are subject to Senate approval.

But their

There is a full sentence (subject+verb) before the comma. After the comma there is subject, verb and complimentary phrase. This means a connector is missing. 1. It is not (A) because it is only a possessive. 2. It is not (B) because with is not a sentence connector. 3. It is not (C) because the second sentence is not a reason to the first. 4. It is (D).