Why could the formation of a hole in the ozone layer cause concern?

Because it can damage the protective layer in the earth's atmosphere, therefor causing a risk of high damage from meteorites and asteroids.

Explanation:

The formation of a hole in the ozone layer would cause concern because it increases the amount of ultraviolet rays that reach Earth and can harm it's inhabitants.

1. (1.2kw)x(15/60hours) = .3kwh --> a

2. (5kw)x(90/60hours)x(8cents/kwh) = $0.60 --> d

3. microwave --> 1200 watts = (1.2kw)x(6/60hours) = .12kwh

coffee-maker --> 900 watts = (.9kw)x(10/60hours) = .15kwh

therefore, it requires more energy for the coffee-maker to do the same amount of work.

so the answer is a.