Answer: a) b), c) are discrete variables and d) is continuous variable.
Step-by-step explanation:
A continuous variable are those whose value is taking by measuring.
A discrete variable are those whose value is taking by counting.
So, a) Number of injuries sustained in a fall is done by counting - Discrete
b) Fraction of birds in a large sample infected with avian flue virus is done by counting - Discrete
c) Number of crimes committed by a randomly sampled individual is done by counting - Discrete
d) Logarithm of body mass is done by measuring - Continuous
Hence, a) b), c) are discrete variables and d) is continuous variable.