Which of the following is crossed aldol product in the reaction ?
${\mathrm{CH}}_3\mathrm{CHO}+{\mathrm{CH}}_3{\mathrm{CH}}_2\mathrm{CHO}\frac{{\mathrm{OH}}^{-}}{{25}^{\circ }\mathrm{C}} \text{'}\mathrm{P}\text{'}.$

When aldol condensation is carried out between two different aldehydes and / or ketones, it is called cross aldol condensation. Given reaction is an example of cross aldol condensation.

${\mathrm{CH}}_3\mathrm{CHO}+{\mathrm{CH}}_3{\mathrm{CH}}_2\mathrm{CHO}\underset{{25}^{\circ }\mathrm{C}}{\overset{{\mathrm{OH}}^{-}}{\to }}{\mathrm{CH}}_3\mathrm{CH}\left(\mathrm{OH}\right){\mathrm{CH}}_2\mathrm{CHO}$