49. explain why all the wavelengths cannot enter the earth's atmosphere?

All the wavelengths can not reach the earth's surface always.

Explanation:

Most of the time the atmosphere absorbs the Infrared radiation from the space.  For this reason, infrared radiation can not reach the earth always. It is basically absorbed by the Co2 and water vapor present in the atmosphere.

correct answer: understand the different control methods available

integrated pest management is an strategy that is based on the ecosystem and try to prevent the pest and the damage caused by them by applying combination of technique like habitat manipulation, biological control and use of resistant varieties.

the main aim of the integrated pest management is not to completely eliminate the pest but to strengthen the ecosystem so that conditions are favorable for plants and unfavorable for pests.