1. Which of the following is always single-stranded?

a. messenger RNA (mRNA)
b. double-stranded RNA (dsRNA)
c. DNA
d. DNA and RNA

(obviously its not b.)

2. Which of the following is a difference between DNA and RNA?

a. most types of RNA are double-stranded
b. RNA contains lipids
c. they have different sugars
d. RNA has thymine

3. Which of the following bases are found in RNA but not in DNA?

a. uracil
b. guanine
c. adenine
d. cytosine

I'm pretty sure 3 is a. but I want to be sure.