(1)Many animals, including some insects, use visual clues to find their way. (2)For example, the female digger wasp lays eggs in a burrow in the soil. (3)She then flies off to capture her prey, which she stores in the burrow to feed her offspring when they hatch. (4)The famous animal-behavior scientist Niko Tinbergen studied the cues used by the female to relocate her burrow. (5)While the female was inside, Tinbergen surrounded the nest with pine cones. (6)When the wasp emerged, she flew around the nest before departing. (7)While she was gone, Tinbergen moved the cones about a foot away. (8)The returning wasp still sought her nest within the ring of cones. (9)Although the nest was in plain sight nearby, she was unable to locate it because the visual landmarks on which she relied had been shifted.

(10)Birds may also use landmarks, such as rivers and seashores, to find their way. (11)Several species migrate at night or over large expanses of ocean, using the position of the sun or stars to tell direction. (12)Many species seem to have genetically programmed information about the direction of the sun at various times of day, and also possess a biological clock that measures off a roughly twenty-four-hour day. (13)Other birds have the remarkable ability to “read” the night sky. (14)Indigo buntings, for example, seem to have a built-in star map that enables them to find which direction is north, during spring migration, by looking at the stars.

Question5. The central idea of the passage is stated in

a. sentence 1.

b. sentence 2.

c. sentence 9.

d. sentence 10.