Consider the following statements about snakes and identify the incorrect one…

Concept

Snakes cannot chew because they lack flat, grinding molar teeth and any chewing musculature. Their lower jaw halves are joined by a stretchy ligament rather than fused bone, so the jaws can spread wide and move independently, a mechanism known as cranial kinesis. Sharp, backward-curving teeth, and in venomous species specialised fangs, grip and pull prey inward while the elastic jaw lets the snake swallow it whole.

Application

1. "They swallow their food whole" matches the jaw-kinesis mechanism described above, so this is a true statement about snakes.

2. "Snakes have sharp teeth" also matches: their teeth are thin and curve backward to grip prey, which is accurately described as sharp, so this is true.

3. "Poisonous snakes have fangs" is true as well: venomous species carry enlarged, hollow or grooved teeth connected to venom glands. Here "poisonous" is used in its everyday sense for a venom-injecting snake, not in the stricter biological sense reserved for organisms harmful only if touched or eaten, so this statement holds under the sense intended by the question.

4. "They chew up their prey" contradicts the concept above. With no molar teeth and no chewing muscles, a snake cannot grind food; it can only grip prey and swallow it whole. This statement is false, which makes it the incorrect one the question asks for.

Cross-check

Snake anatomy confirms this independently: unlike mammals, snakes have no bony chin joint fusing the two halves of the lower jaw, which is exactly what allows the jaws to walk prey down the throat instead of biting off and chewing pieces of it.

Hence, the statement describing snakes as chewing their prey is the incorrect one among the four.