How many hydrogen atoms are attached to each carbon adjacent to a double bond? nurition?

That depends. there are 2 possible answers.
      H
C - C = C - H gives a different answer on the right than on the left.

One the left side, the second Carbon is attached to a double bond and has but one hydrogen attached to it.

The Carbon on the right of the double bond has 2
     H
C- C = C - H
            H

I'm not sure what you should put. It's one of those things that I would repeat my argument and submit it.

Each names a given number of objects

Answer : option a) 84explanation :

considering the question as per the attachment

here we can see that the radon nuclide has 222 as the atomic mass number and 86 as the atomic number.

when it undergoes nuclear fission it gives polonium which has atomic mass number as 218 and atomic number will be 84 along with a helium nucleus which has 4 atomic mass number and 2 as its atomic number.

222 = 218 + 4 (atomic mass number)

86 = ? + 2; therefore ? = 86-2 = 84.

the atomic mass number of polonium will be 84.