Woese proposed a new classification system in 1990.What was different about his system?
A. It included the addition of a new level called “kingdom”
B. It included the addition of a new level called domain
C. It included the removal of the level called kingdom
D. It included the removal of the level called domain

Answer is B.) it includes the addition of the new level call "Domain".

Explanation:

i guessed and got it right

answer; i believe that the correct answer is(d) nondisjunction during meiosis;

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.