Can we compare the vapour pressure of solutions whose concentrations and temperature is known?
The point of the question is to test your understanding
i. of Raoult's law (that increasing the solute concentration decreases the vapor pressure and that the identity of the solute is not important in an ideal solution; the mole fraction of solute determines $\Delta p$: $\Delta p = p-p^\circ = -\chi_\textrm{solute}p^\circ$
ii. that vapor pressure increases with T
Other things you might want to remember are that molality and molarity are linearly proportional for dilute solutions (ie then $m \propto c_M$), and that ideality is approached for dilute solutions of small solutes (typically at low $\pu{mM}$ concentrations such as in this problem).
You can answer the question based entirely  on consideration of the van't Hoff factor to compute total concentrations, and by assuming that the vapor pressure increases with T.
First compute effective total solute concentrations $im$ (equal to either the solute concentration for a non-dissociating solute such as sucrose, or the total ion concentration for the electrolyte solutions):
$$\begin{array}{|c|c|c|} \hline \text{species} &amp;T (\pu{^\circ C})&amp; c_M (\pu{M})&amp; i &amp; ic_M(\pu{M}) \\\hline  1.~\ce{NaCl} &amp; 50 &amp; 0.02 &amp; 2 &amp; 0.04\\ 
2.~\text{sucrose} &amp; 15 &amp; 0.02 &amp; 1 &amp; 0.02\\ 
3.~\ce{CaCl2 } &amp; 15 &amp; 0.005 &amp; 3 &amp; 0.015\\ 
4.~\ce{CaCl2 } &amp; 50 &amp; 0.005 &amp; 3 &amp; 0.015\\\hline  
\end{array}$$
Inspection should quickly eliminate all options but row 4 since they have a higher effective concentration at the same T, or since they are at a lower T at the same effective concentration.
Actual vapor pressures are not stated in the problem. In the absence of that information there is no point in attempting to compare things in more detail, and that's not the point of the problem. However, provided Raoult's law holds it can be used to determine the change in vapor pressure regardless of T. Raoult's law assumes the identity of the solute does not matter, that the effect of added solute on the activity of solvent is entirely entropic (accounted for by ideal mixing entropy) and that the gas is ideal. In general, to predict vapor pressure at any T and solute concentration you need a model of the activity of the solvent as a function of the solute concentration, and of the activity in the gas phase. You can determine the vapor pressure by finding the conditions that render the activities identical.