Which of the following is always correct?
A. Cross product of two countable set is countable
B. Cross product of two countable set is uncountable
C. Cross product of two uncountable set is countable
D. Cross product of uncountable and countable set is uncountable
E. Cross product of uncountable and countable set is countable
F. Cross product of uncountable and countable set is uncountable