Why heat trapping by CO2, CH4 etc in the atmosphere is called ‘green house effect’?

Q. Why heat trapping by CO2, CH4 etc in the atmosphere is called ‘green house effect’?

A.            Garden Green house is permeable to both heat and sunlight

B.            Garden Green house is impermeable to sunlight

C.            Garden Green house is permeable to sunlight and impermeable to heat

D.            Garden Green house is impermeable to both sunlight and heat

Answer: Garden Green house is permeable to sunlight and impermeable to heat