Cheetahs can run extremely fast because:. a. They are competing with stronger lions and hyenas for their food, so they need to be fast
b. Their ancestors who were able to run fast had an advantage and passed those genes on to their offsprings
c. They need to outrun lions
d. All of the explanations are correct
e. Over time, they gradually built up speed as they adapted to faster and faster prey species

white blood cells or wbc s are mainly 2 types-

1.agranulocytes

2.granulocytes

the monocytes or macrophages of agranulocytes , dendritic cells which are accessory leucocytes, and b cells which is one type of lymphocytes   identify the antigens present on the pathogen's surface. these three cells are called antigen presenting cells(apc) which are phagocytes and destroy the antigens by secreting antitoxins. besides this leukocyte is always plays vital role in the immunity of the body.

the correct answer: the index of refraction of the second medium is lower i tried this persons answer and it was wrong this person is lying