Where are macrophages found in the body?
i. blood
ii. infected tissues
iii. lymph nodes
a.i only
b.ii only
c.iii only
d.ii and iii only
e.i, ii, and iii

D.II and III only

Explanation:

Monocytes are the agranular leukocytes that serve as precursor of macrophages. When the blood monocytes enter the infected tissue or the site of infection, they are transformed into macrophages to carry out the function of phagocytosis of pathogens and cellular debris. Macrophages are also present in lymphoid tissues such as spleen and lymph nodes to remove the debris and pathogens from the lymph. Hence, macrophages are found in lymph nodes and infected tissues only; not in blood.

An organisms niche is (A) The range of physical and biological conditions in which an organism lives and the way in which it uses those conditions.
 Technically, any of the answers could be true, however, A is the only one that offers a broad definition.A niche is not only the location and conditions in which an organism lives, but also the organisms role within that niche and how it uses the resources to survive.