Answer:
Examples of complex compound include potassium ferrocyanide K4[Fe(CN)6] and potassium ferricyanide K3[Fe(CN)6]. Other examples include pentaamine chloro cobalt(III) chloride [Co(NH)5Cl]Cl2 and dichlorobis platinum(IV) nitrate [Pt(en)2Cl2](NO3)2.
To identify in what beakers will a reaction occur, we need to know what aqueous solution is in the four beakers. Then, we also need to know what metals are placed inside those beakers. Now, we can analyze which metals might or will react to the solution in the beakers.