Find the odd one out A, B, C, or D

Bài 1. Find the odd one out A, B, C, or D.
Question 1: A. affect
B. replace
Question 2: A. density
B. overcrowded
B. hunger
Question 3: A. explosion
Question 4: A. space
B. safely
Question 5: A. criminal
B. driver
Question 6: A. solar
B. wind
Question 7: A. plane
B. train
Question 8: A. trash
B. garbage
Question 9: A. death
B. extinction
C. effect
C. crime
C. slum
C. poverty
C. doctor
C. water
C. bus
C. waste
C. survival
D. fly
D. megacity
D. float
D. slum dog
D. student
D. storm
D. cab
D.
recycle
D. mortality