Answer
a. Tin
b. Gallium
c. Cannot be predicted using periodic table
d. Tin
Work Step by Step
Atomic radius increases as we move down the periodic table. Hence Tin, Gallium and Tin are expected to have greater atomic radii as compared to Silicon, Bromine and Selenium, respectively.
For the pair of Tin and Bismuth, they are located in different periods. Tin is one row down from Bismuth (increase in atomic radius), however, it is right from the Bismuth (decrease in atomic radius), hence we cannot predict it using our current knowledge.