Science

You can't skip mathematics in class 10th.

Yes,in todays era both are considered at equal level.Only B tech from IIT and NIT is considered at higher level.

Hi Priya
Little confusion at this stage is perfectly okay as you have advices and suggestions coming from all corners (read, relatives, cousins, uncles and friends). If you wish to go in the field of investigation there could be various paths like B.Sc Forensic Science, Investigative journalism, News Reporting, RAW or IB but you need to be very strong physically, emotionally both.
Another option is research, where you are investigating about may be people, data, numbers or things. Do make a check if your skills match up or not.

Hey, read below link :
http://hyperphysics.phy-astr.gsu.edu/hbase/biology/celres.html
There is a very good description along with diagrammatic representation of respiration and it's two types i.e. aerobic and anaerobic respiration.
Hope it helps.

It will be difficult to advice you without details of of your education details. You are requested to share your educational details for right advice.

With BSc degree you are eligible for majority of non technical posts in Government (Central, State, PSU, Banks etc) where eligibility criterion is graduation degree. Beside this you may able to get job of technician, lab assistant in Scientific R&D organisation. You are also eligible to do BEd and take school teacher job. In order to have better career growth you will have to do post graduation.