Correct Answer - A
`Li^(+) (0.76 Å)` is much smaller than the other ions `[Na^(+) (1.02 Å), K^(+) (1.38 Å), Rb^(+) (1.52 Å), "and" Cs^(+) (1.67Å)]`. For this reason, Li only mixes with Na above `380^(@)`. It is immiscible with the metals K, Rb and Cs, even when molten. Even Li does not form substitutional alloys with them. In contrast, the other metlas Na, K, Rb, and Cs are miscible with each other in all proportions.
