Which of these statements best describes a scientific theory? it is a description of an observation which does not change over time. it is a description of an observation after research over a period of time. it is an explanation for an observation which is not based on data. it is an explanation for an observation after several valid experiments?

The correct answer is- It is an explanation for an observation after several valid experiments.

A scientific theory can be described as an explanation of a fact that can be tested and verified with the help of repeated experiments, using particular protocol of experiment that involves measurement, and evaluation of results.

In other words, It is the interpretation and explanation of the facts that are observed through various experiments.

Thus, it is an explanation for an observation after several valid experiments.

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.

nucleic acid molecules are incredibly complex, containing the code that guarantees the four different nucleotide units comprise dna, the nucleic acid of interest to the genealogist. and one of four nitrogen-containing molecules called nucleotides