Which statement is true?
a) Tides occur about an hour later each day.
b) Tides occur at the same time each day.
c) Tides occur about an hour earlier each day.
d) Tides do not happen at set times.
P.S: I think the answer is letter d, but I am not 100% sure. This is for science, but they do not have a science category, so I am just putting it as Social Studies.