Concept:Venus is called Earth's "sister planet" because its size and mass are very close to Earth's.Explanation:Earth's diameter is about 12,742 km. Venus has a diameter of about 12,104 km, making it nearly the same size. In contrast, Mars is roughly half Earth's size (6,779 km), while Saturn and Jupiter are gas giants many times larger (116,460 km and 139,820 km respectively).Answer:D. Venus