Completing inorganic reactions and writing spectator ions
For B, you have correctly identified calcium phosphate as the precipitate, as it is the least soluble of all possible compounds. In the case of A, cobalt phosphate precipitates from the solution containing cobalt(II) and phosphate salts.

$$\ce{3Ca^{2+} + 2PO4^{3-} -&gt;~ Ca3(PO4)2\downarrow}$$
$$\ce{3Co^{2+} + 2PO4^{3-} -&gt;~ Co3(PO4)2\downarrow}$$