Question

choose the two sentences in this excerpt that explain why the number of tree hollows is shrinking. inside the holes, the animals raise their young and hide from predators. the cozy homes also protect their inhabitants from snow, rain, and other harsh weather. but the number of tree hollows is shrinking. people are clearing forests to sell the wood or to make space for farms and buildings. in cities, people often cut down big old trees because theyre afraid they might topple or that they will drop branches and hurt someone. scientists are investigating how the loss of tree hollows affects wildlife - and what to do about it. one team in australia found that birds and small mammals may be fighting over scarce hollows in cities. scientists in south america learned that its important

Explanation:

The sentences that explain the shrinking number of tree - hollows are those that mention human actions causing the reduction. People clearing forests for wood or to make space for farms and buildings, and cutting down big old trees in cities due to safety concerns are the reasons.

Answer:

1. People are clearing forests to sell the wood or to make space for farms and buildings.
2. In cities, people often cut down big old trees because they're afraid they might topple or that they will drop branches and hurt someone.