Spring tides occur during

Options

A. a full-moon day
B. a new-moon day
C. the first and last quarter phases of the moon
D. Both (a) and (b)

Answer

### Step-by-Step Solution:

1. **Understanding Tides**: Tides are the rise and fall of sea levels caused by the gravitational pull of the Moon and the Sun on the Earth.

2. **Identifying Spring Tides**: Spring tides are characterized by higher high tides and lower low tides. They occur when the gravitational forces of the Moon and the Sun align.

3. **Conditions for Spring Tides**: Spring tides occur during two specific lunar phases:
- **New Moon**: This is when the Moon is positioned between the Earth and the Sun. The gravitational pull from both the Moon and the Sun combines, leading to higher tides.
- **Full Moon**: This is when the Earth is between the Moon and the Sun. Again, the gravitational forces align, causing similar effects.

4. **Conclusion**: Therefore, spring tides occur during both the new moon and the full moon phases.

5. **Answer**: The correct answer is both A (full moon day) and B (new moon day).