$C_6{H}_{5}CHO+C_6{H}_{5}COC{H}_3\stackrel{O{H}^{-},293K}{\to }X$ 

IUPAC name of cross condensation product X 

Cross aldol condensation reaction is type of reaction in which two aldehyde or ketone combine to form a alcohol and carboxylic acid upon acidic hydrolysis. 

$\underset{\mathrm{Benzaldehyde}}{{\mathrm{C}}_6{\mathrm{H}}_5\mathrm{CHO}}+\underset{ \mathrm{Benzophenone}}{{\mathrm{C}}_6{\mathrm{H}}_5\mathrm{COC}{\mathrm{H}}_3}\stackrel{{\mathrm{OH}}^{-},293\mathrm{K}}{\to }\underset{1,3–\mathrm{diphenylprop}–2–\mathrm{en}–1–\mathrm{one}}{{\mathrm{C}}_6{\mathrm{H}}_5\mathrm{COC}={\mathrm{CHC}}_6{\mathrm{H}}_5}$ 

  Hence, correct answer is option (C) 1,3–diphenylprop–2–en–1–one.