PT 2 S2 Q4

Dried grass clippings mixed into garden soil gradually decompose, providing ... ...

Which one of the following, if true, most helps to explain the difference in plant growth described above?
(A) The number of beneficial soil bacteria increases whenever any kind of plant material is mixed into garden soil.
(B) ...
(C) ...
(D) ...
(E) ...

*This question is included in Practice Set: "Resolve/Explain" Questions, Set 1