Answer:
The correct option is;
A). Randomized block design
Step-by-step explanation:
In a randomized block design the experimental units or subjects of the experiment are separated into subgroups known as blocks with the property that the the variability (difference) of the parameters within the blocks are lesser than the variability between block, such that the treatment of the research or experiment are assigned differently to each block
The groups can therefore comprise of the following;
Group 1
15 men and 15 women to perform water aerobics for 30 minutes twice a week
Group 2
15 men and 15 women to perform water aerobics for 60 minutes once a week
Therefore, the effect of the experiment will be much less attributed to gender than to the durations of the water aerobic exercise.
