In most cases, adaptive immune responses rely on the initial activation of in secondary lymphoid tissue:

This question lacks options, options are: a. macrophages

b. T cells

c. B cells

d. dendritic cells

e. epithelium

The correct answer is c.  

Explanation:

In the secondary lymphoid organs is where foreign substances or antigens are presented and the specific immune response begins. They are the lymph nodes, spleen, and MALT. The main function of B cells is the recognition of foreign molecules to the body, called antigens, and the production of specific antibodies to neutralize them. After maturation, B cells are central cells in the adaptive immune response, they agglomerate in the lymph nodes, spleen and other lymphoid tissues, where they will come into contact with the antigens for which they are specific.

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.

hydrogen is a compound or a single element and a element is a pure substence that cannot be separated into simpler subtances

clorine is a compound its a chemical substance that forms when two or more different elements combine

so both hydrogen and clorine are compounds