Smallest man-like ape is

The correct answer is A, Gibbon.

Apes are divided into lesser apes (gibbons and siamangs, family Hylobatidae) and great apes (family Hominidae). Gibbons are the smallest apes, usually weighing around 4 to 8 kg, and they are arboreal brachiators with long arms. Chimpanzees, gorillas and orangutans are all great apes, and the gorilla is the largest living primate.

• Chimpanzee (B): a great ape, far heavier than a gibbon. Its genus Pan, along with bonobos, is the closest living relative of humans.
• Gorilla (C): the largest living primate, with adult males often exceeding 150 kg in the wild, so it sits at the opposite extreme.
• Orangutan (D): the only Asian great ape, found in Borneo and Sumatra. It is a large, mostly solitary arboreal species, not the smallest.

The core concept is the classification of hominoids, which matters for Mains questions on human evolution and primate biodiversity. The superfamily Hominoidea includes both lesser and great apes, and humans belong to it too.

Trap: candidates pick chimpanzee because it is the closest relative of humans. Phylogenetic closeness and body size are different questions, and this one asks only about size.