Tides and lunar effects: Identify the correct combined statement about spring tides, neap tides, and tidal periodicity.

Introduction:
Tides are driven by the gravitational interaction of the Moon and the Sun with Earth, modulated by Earth's rotation. The question tests basic but essential tidal facts for coastal engineering and navigation.

Given Data / Assumptions:

• Semidiurnal or mixed tidal regimes are considered.
• New/full moon alignment (syzygy) and first/third quarters (quadrature) are standard lunar phases.
• Lunar day duration is about 24 hours 50 minutes.

Concept / Approach:
During syzygy (new/full moon), lunar and solar tidal forces align, producing spring tides (higher highs, lower lows). At quadrature, forces partially cancel, producing neap tides (reduced range). The timing of successive high waters follows the lunar day, hence the ~50-minute daily shift.

Step-by-Step Solution:
Confirm spring tides at syzygy → statement a true.Confirm neap tides at quadrature → statement b true.Recognize typical ratio of spring to neap ranges ≈ 2:1 (site-dependent) → statement c broadly true.Acknowledge tidal periodicity is tied to the lunar day (~24 h 50 min) → statement d true.Therefore all statements collectively are correct.

Verification / Alternative check:
Tide tables and harmonic analysis show spring–neap modulation and the 50-minute daily lag consistent with lunar forcing.

Why Other Options Are Wrong:
Any single statement alone is incomplete; the combined option best represents tidal behavior.

Common Pitfalls:
Assuming spring tides occur only once a month (they occur near both new and full moon) and ignoring site-specific amplification by resonance and bathymetry.

Final Answer:
All of the above.