7. which statement best describes the source of the sun's energy?
a. hydrogen fuses to form helium.
b. protons merge with electrons to form neutrons.
c. oxygen combines with elements in the sun.
d. the high temperature of the photosphere produces radiation.

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.