In an experimental procedure, the researcher has established multiple levels of a chemical, or amounts of light, or some other factor at the beginning of the experiment, in order to determine if and how much the biological system responds. the manipulated factor at varying levels is the

The correct answer is the independent variable.

Explanation:

An independent variable signifies a variable, which is supervised or changed in a scientific experiment. It signifies the reason or causes of an outcome. The independent variables refer to the variables, which are changed or manipulated by the researcher in order to examine the dependent variable.  

A modification in the independent variable straightforwardly makes a variation in the dependent variable. The influence on the dependent variable is recorded and measured. Thus, it is clear that the manipulated factor at varying levels in the given case is the independent variable.  

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.

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