Spring tides:

a. happen twice a month
b. are caused by the gravitational pull of the sun and the moon
c. occurs when the earth, sun, and moon are aligned
d. all of the above

They also happen twice a month, and they occur when earth, sun and moon are alingned.

All of the above

Proof from my section))

Tides occurring during this condition are known as spring tides and happen when the moon phase is new (dark). At the time when the earth, moon, and sun form a right angle, the tide range is at its lowest level. These tides are called neap tides. A lunar month of 28 days consists of two spring tides and two neap tides.

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