Spring tides occur ______. Multiple Choice once a month when the Earth-Sun and Earth-Moon lines are at an angle of 45o to each other twice a month when the Earth, Sun and Moon are fully aligned once a month when the Earth-Sun and Earth-Moon lines are at a right angle to each other twice a month when the Earth-Sun and Earth-Moon lines are at a right angle to each other once a month when the Earth, Sun and Moon are fully aligned