Which of the Following Statements About Orbital Symmetry and Cycloaddition

Which of the following statements about orbital symmetry and cycloaddition reactions is true?

A) Thermal cycloadditions involving an odd number ofp bonds proceed by an antarafacial pathway.
B) Thermal cycloadditions involving an even number ofp bonds proceed by a suprafacial pathway.
C) Photochemical cycloadditions involving an even number ofp bonds proceed by an antarafacial pathway.
D) Photochemical cycloadditions involving an even number ofp bonds proceed by a suprafacial pathway.