Question

If lines ab and cd are parallel, which of the following statements are true?
Check all that apply.

A. Ab and cd are skew lines
B. Ab and cd are perpendicular
C. Ab and cd intersect at a single point
D. Ab ll cd
E. Ab is perpendicular to cd
F. Ab and cd are coplanar

Answer 1

If lines ab and cd are parallel, the following statements that are true are letters D, F. 
D. Ab ll cd 
F. Ab and cd are coplanar
The rest of the choices do not answer the question above.

Answer 2

The correct answers are:
(D) ab ll cd 
(F) ab and cd are coplanar

Explanation:
The symbol for parallel is " ll ". Therefore, if we translate the given sentence, ab and cd are parallel, into the Mathematical terms, we can write it as:

ab ll cd (Option D)

Where ab = line
cd = line

Furthermore, the lines ab and cd are coplanar because they form the plane. In other words, you can say that the lines ab and cd lie on the same plane. (Option F)

Hence the correct answers are:
(D) ab ll cd 
(F) ab and cd are coplanar