Which energy source is the result of tiny sea creatures being compressed over million of years?

Extreme pressure in the sea is the energy source that resulted in compression of tiny sea creatures into fossils, over millions of years. These creatures got buried under the ocean or river sediments, and the pressure caused their compression, leading to the formation of oil and natural gas.

Explanation:

a. "to practice" is the best phrase to complete the sentence.

explanation:

during the summer, she likes to practice her soccer skills so that she is ready to play in the fall.

(note that : all the other options "the practicing of", "practice for" and "to do a practice on" are inappropriate as they make the sentence grammatically incorrect.)

c. in order of atomic number