http://i65.tinypic.com/xqdkjs.jpg - Question 23 why is the answer (c)..?

23.
A. False
If Y is an alkali metal (Group I metal), the density is low, the melting point is low, and the formula of its oxide is Y₂O.

B. False
If Y is a metal in Group III, the formula of its oxide is Y₂O₃ and the colour of the Y₂O₃ is white.

C. True
Density and melting point of a transition metals are high. A transition metal has variable oxidation number (oxidation state). All these fit the data.

D. False
No information is available to show whether the oxides of Y is amphoteric or not.

...... The answer is: C. Y is a transition metal.