Cfc, freon, and aerosols are becoming less commonly used because they
a) cause acid rain.
b) harm the ozone layer.
c) have radioactive waste.
d) cause alzheimer's disease.

Answer : The correct option is, (B) Harm the ozone layer.

Explanation :

CFC and Freon are used as refrigerant gases and as propellants in aerosol sprays. And the aerosols is a suspension of fine liquid or solid particles in the gas.

When CFC, Freon, and aerosols reaches to the stratosphere region, the UV light affects them and they release chlorine atoms. And the chlorine atoms break down the ozone molecules and harm the ozone layer. The ozone layer is useful to us because it protect us from the U.V rays which are the harmful rays.

Hence, CFC, Freon, and aerosols are becoming less commonly used because the harm the ozone layer.

answer: at 24 february, 2014 the population gets twice of its initial population.

explanation:

since we have given that

the population for alpha city, t years after january 1, 2004 is given as

first we find out the initial population, i.e. t=0,

so, our quadratic equation becomes,

according to question, we have said that if the population has twice its initial population, then it becomes

so, time taken to reach this above mentioned population is given by

now, we know that time can't be negative so, we take t=9.149 years.

hence, at 24 february, 2014 the population gets twice of its initial population.