Hello Aspirant,
Biochemistry and Microbiology are really good fields.
Biochemistry is all the chemistry in your body.  In this you learn about the composition of cell, you learn about enzymes, proteins, lipids , carbohydrates , mechanisms of respiration, excretion , digestion and not only this you will also learn about various mechanisms in plant system such as physiology of photosynthesis respirations and many more. If you want to know about chemistry in your body this is surely the one you must choose.
After doing Bsc biochemistry you can be a dietitian,  chemist, nutritionist you can go in RnD and many more.

In Microbiology, you will learn about microbes and their importance and also the micro life around us. Quite interesting subject to choose.
There are lots of scope in microbiology, its a new upcoming field and there's lot of scope in research.  And it goes without saying there's scope in everything you are interested in.

In Bsc first year there are lot of combinations of three subjects you can choose between them. Like if you want to do plain Bsc tgen you have combinations like CBZ( Chemistry, Botany,  Zoology ) , PCB( Physics,  Chemistry,  Botany) ,  PCZ( Physics, Chemistry, Zoology) , CBMICRO( Chemistry , Botany, Microbiology) , CBBIOCHEM(Chemistry, Botany, Biochemistry) , CBLS( Chemistry, Botany, Lifescience) ,  CZLS ( Chemistry, Zoology, Lifescience) and many more.  These combination depends on the college you choose. Different colleges have different combinations.  All these combinations mentioned above are only for first year. And rest depends on the college.
Hope this answers your questions. Thank you.