Answer:
A
The nuber of each one should be same
Calcium Chloride is the salt that is effective for melting ice on roads
Solid carbon reacts with oxygen gas to form carbon dioxide gas.
The balanced chemical equation for this reaction:

Compound A : SnCl2
the mass ratio of Cl and Sn: 71 g Cl/ 119 g Sn = 0.579 g Cl/ 1 g Sn
Compound B: the ratio of mass of chlorine per 1 g Sn is twice the ratio of chlorine per 1 g Sn in compound A => 1,194 g Cl/ 1 g Sn = 142,086 g Cl/ 119 g Sn
=> the number of chlorine/ 1 atom Sn = 142.086/ 35.5 = 4.
=> the formula of B: SnCl4