A boy picks up an earthworm and place it on a white tile. He observed that the earthworm has difficulty in moving forward. Explain why.​

A number of tiny hair like bristlez are present on the lower surface pf an earthworm's body. These bristles help it to get a good grip on the surface of q ground.However these bristles donot provide good grip on plain glass tiles.

Earthworms have microscopic hairs or bristles all over their body which provide the necessary traction while movement. These bristles or setae are present on each segment of their body and it imparts the necessary grip or anchorage for forward and backward movement.

Tile is smooth in nature so earthworms cannot move as the setae will not get sufficient surface support to move the body.

Answer From Gauth Math

i'm thinking (a) to keep sand in place; ////////////

explanation: a sand fence or sandbreak, like a snow fence, is used to force windblown, drifting sand to accumulate in a desired place. sand fences are employed to control erosion, sand dune stabilization, keep sand off roadways, and to recruit new material in desert areas.