Humus creates good soil tilth, which is an indirect benefit of microorganism action.

The correct answer will be-true.

Explanation:

Humus is the dark matter of the soil composed of the dead organisms and the micro-organisms which increases the organic matter of the soil.

The soil tilth is the physical property of the soil which is helpful for seedling emergence and root penetration due to large pore spaces for water movement and air filtration.

Since humus acts as a source of nutrients to plants as well it increases the porosity of the soil which indirectly improves the tilth of the soil therefore true is the correct answer.

the element that provides strength to the exoskeletons of clams and oysters is phosphorus. this is so because calcium carbonate is the main component in the shells.

explanation:

the correct answer is option b

behavioral response need communication and thus co-ordination at several levels such as interaction among cells, organ system and the entire organism.

behavioral response produces both internal and environmental stimulus.