4. Which is an example of a species
a) Big Fish
b) Insects
c) Cricket
d) Small Dog

insects

Explanation:

There are variety of insects and is considered a species. A big fish is just a description so is small dog. And cricket is simply just cricket.

carbon atoms, hydrogen, oxygen, and nitrogen.

before, trains worked using the steam engine. thus, it uses heat so it is crucial to apply heat balance. the steam engine absorbs energy during the stage of boiling water. so, this is the endothermic reaction. when the steam is used to work the piston, it has to release this energy through running the train. the excess energy is released as an exhaust to the chimney. this is the exothermic process because it releases energy to the surroundings.