Which muscles in the skin contract to make the hairs on our skin stand up straight (goose bumps) when we are cold or frightened ?

Arrector pili

The correct answer is Option (4) -Arrector pili

The muscles in the skin that contract to make the hairs on our skin stand up straight (goosebumps) when we are cold or frightened are called: Arrector pili

Arrector pili muscles are small muscles attached to hair follicles in the skin. When these muscles contract, they pull on the hair follicles, causing the hairs to stand upright. This contraction of the arrector pili muscles is a response to cold temperatures or emotional stimuli such as fear or anxiety. The raised hairs create a layer of insulation on the skin, trapping a layer of air close to the body to help conserve heat. This response is commonly known as piloerection or goosebumps.