Answer:
letter B
none zero digit are significant figures
Not sure but just coming to say good luck and take your time
-- 'Ca' (Calcium) is an element.
-- The proton has a positive charge.
-- Nuclear fusion results in the synthesis of atoms of new elements.
-- H₂O (water) is a chemical compound.
-- Nuclear fission is a decay of the nucleus.
-- The atomic number of an element is the number of protons
in each atom of it.
-- I suppose you're using the Greek letter <span>η ('eta', not 'nu')
to represent the neutron.
-- I suppose you're using ' e ' to represent the electron.
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The train travells at he speed of 225 km/2.5h
now
225km=225000m
2.5 hr=150min=9000s
=>avg sp of train is=225000/9000s=25m/s