Could someone check the answer please.

I just took a test and was wondering if someone could check a few of my answer. If they are wrong could you give me a brief explanation. My answers are after the question. Thanks

1. Which of the following is a countably infinite set.

a) Real Numbers

b) Integers

c) Rational numbers

d) Irrational numbers

e) Complex number

Answer a

2) Statement r is true while s is false.

Which is false?

Answer C

3) Which of the following statements is logically equivalent to ?

Answer D

U 1,2,3...12 A=2,4,6,8,10 B=1,3,5,7,9 C=1,2,3,4

Which of the following set is specified by where x denotes that c is a complement of x

1,2,3,4

11,12

0

1...9

5...12

Answer B