In the lunar cycle, the highest tides, known as "spring tides," occur during the full moon and new moon phases. Based on typical lunar phase diagrams:
- Phase 1 (New Moon): The moon is between the Earth and the Sun, leading to higher tides.
- Phase 2 (First Quarter): The moon is at a right angle with respect to the Earth and Sun, leading to lower tides.
- Phase 3 (Full Moon): The Earth is between the sun and the moon, again leading to higher tides.
- Phase 4 (Last Quarter): Similar to Phase 2, this results in lower tides.
Therefore, the tides are highest during Phase 1 (New Moon) and Phase 3 (Full Moon). If you need to choose only one answer, it would depend on which phase is represented in your diagram. Without seeing the diagram, I would recommend checking if Phase 1 or Phase 3 corresponds to either of these phases.