5. A set of 3 parallel lines on a plane intersects with another set of 5 parallel lines, the number of parallelograms that can be formed is ( ).
(A) 24
(B) 28
(C) 30
(D) 32
5.C.

Selecting any two lines from one group and any two lines from another group can form a parallelogram. The number of ways to choose any two lines from three parallel lines is 3, and the number of ways to choose any two lines from five parallel lines is 10. Therefore, the number of parallelograms is $3 \times 10=30$.