Sister chromatids present during mitosis are
a. duplicated chromosomes.
b. identical copies.
c. separated during mitosis.
d. made during the s phase.
e. all of the above.

The correct answer is e. All of the above.

Explanation:

Sister chromatids are made during the synthesis phase of the cell cycle. In the synthesis phase, the homologous chromosomes get replicated and sister chromatids are produced so they are produced by duplication of chromosomes.  

As sister chromatids are produced by replication, therefore, they are identical copies of parent chromosomes. These sister chromatids are joined to each other at centromere. They get separated during the anaphase of mitosis and moves to the opposite pole.

Therefore the right answer is e.

Chemically & Physically(mechanically)

Explanation:

Weathering is the wearing away of rock found at the surface of the earth. There are different ways weathering can occur and they include;

1. Mechanical weathering: This is the breakdown of rock into bits or fragments. Physical factors such as water can lead to this breakdown. When water falls into the pores and cracks of rocks, pressure can be created that will eventually result in the breakdown of these rocks.

2. Chemical weathering: This type of weathering causes a change in the physical makeup of the rock. The new form of rock created is more prone to erosion. Temperature is factor that can speed up chemical weathering.