Factorising expressions I

This task is about factorising algebraic expressions.
a) x2 + 9x + 18 can be factorised to

(A)   (x + 9)(x + 2)
(B)   (x – 6)(x + 3)
(C)   (x + 6)(x + 3)
(D)   (x – 6)(x – 3)
 

b)

x2 + 5x + 4 can be factorised to

(A)   (x + 5)(x + 1)
(B)   (x + 4)(x + 1)
(C)   (x + 5)(x – 1)
(D)   (x + 4)(x – 1)
 

c)

  x2 + x – 12 can be factorised to

(A)   (x – 4)(x + 3)
(B)   (x + 6)(x – 2)
(C)   (x + 4)(x – 3)
(D)   (x – 6)(x – 2)
 

d)

  x2 – 9x + 20 can be factorised to

(A)   (x – 4)(x – 5)
(B)   (x – 10)(x – 2)
(C)   (x – 5)(x + 4)
(D)   (x – 10)(x + 2)
 

e)

  x2 – 10x + 21 can be factorised to

(A)   (x + 7)(x – 3)
(B)   (x – 7)(x + 3)
(C)   (x + 7)(x + 3)
(D)   (x – 7)(x –3)
 

f)

  x2 – 2x – 24 can be factorised to

(A)   (x + 4)(x - 6)
(B)   (x – 4)(x + 6)
(C)   (x – 6)(x – 4)
(D)   (x + 4)(x + 6)