Hello Aspirant!
It actually depends on the college or institute taking the test. If the syllabus for the entrance test clearly states that questions will be asked on microbiology only, then its easy and you can refer to the following books for a strong basic knowledge:
But, my friend, it is highly unlikely that questions will be asked only from microbiology. If you are a Microbiology undergraduate, then you should know that the BSc Microbiology syllabus encompasses other parts such as Genetics, Biochemistry, Biophysical Calculations, Enzymology, Immunology and other subtopics.
So, in order to get a complete grasp of undergraduate biology, you should prefer the following books:
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