Exercise 2 solution

(a) Full Moon: spring tides. Earth is between the Sun and Moon, so the Sun's and Moon's tide-raising forces line up and add together.
(b) First-quarter Moon: neap tides. The Sun and Moon are at right angles as seen from Earth, so the Sun's bulge partly cancels the Moon's, and the range is smallest.
(c) New Moon: spring tides. The Moon is between Earth and Sun, again lined up, so the forces add.

In practice the largest tides usually come a day or two after the exact phase, because of the time the ocean takes to respond.