b. when the sun, Earth, and the moon are nearly in a line
Explanation:
Due to gravitational pull of sun and moon, the level of water in seas and oceans rises above its normal level. This is known as tides. Highest tides occur when the sun, the moon and the Earth align in a straight line i.e. during New moon and Full moon. This is because in this alignment, there is maximum effect of gravity. Tide occurrence during this phase are also referred as spring tides.