Asimilarity between the governments of iran and saudi arabia is that
a. neither allows political parties
b. both are monarchies
c. both have constitutions
d. both of their legal systems use civil laws

D- not true, they actually implement Sharia (at least partially in each country)
C- well, Saudi Arabia has a constitution-like document, but not really a constitution - not the right answer
B- Iran isn't
A- I think this is the best they both banned political parties, at least some of them.

A similarity between the governement of Iran and Saudi Arabia is the neither allows political parties, since that is their system of governement in that particular area.