Given the statement "If a line is horizontal, then it has slope equal to zero," what is its contrapositive? If a line is horizontal, then it has zero slope.
O Ifa line has zero slope, then it is a horizontal line.
O If a line is not horizontal, then it does not have zero slope.
O If a line does not have zero slope, then it is not a horizontal line.

the answer would be a

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.

answerca air mass;