Organisms are constantly interacting with their environment. sometimes this interaction has a positive effect on the environment, other times a negative impact. beetles in the forest infest and eat limbs of trees that have fallen to the forest floor. the best way to describe the beetles impact is to say that

a) they are having a neutral impact on the environment by acting as decomposers.

b) they are having a positive impact on the environment by acting as decomposers.

c) they are having a negative impact on the environment by acting as decomposers.

d) they are having a predatory impact on the environment by acting as decomposers.

The correct answer is option B) i.e. they are having a positive impact on the environment by acting as decomposers.

By acting as decomposers beetles are helping in recycling of nutrients between biotic (organisms) and abiotic factors (enviroment). So, it may be considered as positive impact on the environment. Decomposers play a very important role in food chains and food webs. They breakdown biomolecules and liberate the micronutrients and micronutrients as inorganic molecules back to the environment. These inorganic molecules are used by plants once again  to synthesize biomolecules. This is how nutrient cycle operates with the help of decomposers. For example, protein molecules of dead and decaying matter are broken down by decomposers to liberate nitrogen gas to the environment which is utilized by leguminous plants to make protein molecules again.

9.9 years

a = p(1 + rt) . . account balance after time t at rate r starting with principal p

3000 = 2500(1 + 0.0202t) . . filling in the given numbers

1.2 = 1 + 0.0202t . . divide by 2500

0.2 = 0.0202t . . . subtract 1

0.2/0.0202 = t ≈ 9.901

it will take about 9.9 years for the account balance to reach $3000.