Fact 1: Algae have varied life cycles. Fact 2: Some red algae are eaten by humans. Given the two facts above, something eaten by humans have varied what?

Available choices:
I. story times;
II. commutes;
III. temperature;
IV. Plants growth;
V. energy usage;
VI. life cycles;
VII. bedtimes;
VIII. layers of fat;
The answer is:
VI.