Which two substances are among the four major types of organic compounds made by living things? A. Water
B. Nucleic acids
C. Lipids
D. Carbon dioxide

Parallel lines are lines in a similar plane that will never cross and furthermore If that they are in various planes, those lines will never intersect as well. Equal lines never converge, however they should be in a similar plane. The definition doesn't need the unclear term point, yet it requires plane as they cross one another.

While perpendicular lines are two lines that will meet at a right angle which is 90 degree , these lines must be co-planar; therefore, plane isn't needed in the definition.