"The grass is reluctant to step on it." These slogans remind people not to trample on the lawn, because walking on the lawn often will cause soil hardening.

The respiration of grass absorbs oxygen in the air. Often walking on the lawn will cause soil hardening, reduce soil gaps and reduce oxygen in the soil, and the roots of grass can't breathe, thus affecting the growth of grass. Therefore, you should not walk on the lawn, but protect the grass.

So choose: C.