The correct answer to the question is option 'A', which is Spring tide.

Explanation:
- What is a Spring Tide?
A spring tide is the highest and lowest tide that occurs during the lunar month. It happens when the gravitational forces of the Moon and the Sun align with the Earth.
- Causes of Spring Tide:
During a new moon or full moon, the Sun, Moon, and Earth are in a straight line, which causes the gravitational pull on the Earth's oceans to be at its maximum. This alignment creates a strong gravitational force, resulting in a higher high tide and a lower low tide.
- Frequency of Spring Tide:
Spring tides occur twice a month, during the new moon and full moon phases. Hence, they happen about every 14 days.
- Effects of Spring Tide:
During a spring tide, the difference between high tide and low tide is at its greatest. This can lead to more extreme changes in water levels, affecting coastal areas and navigation. It can also influence marine ecosystems and the movement of marine organisms.
- Spring Tide vs. Neap Tide:
While spring tides have the greatest difference between high and low tides, neap tides have the least difference. Neap tides occur when the gravitational forces of the Moon and the Sun are perpendicular to each other, causing a weaker gravitational pull on the Earth's oceans.
- Other Tide-related Terms:
1. Neap Tide: The tide with the least difference between high and low tides.
2. Lunar Tide: Another term for the tides caused by the gravitational pull of the Moon.
3. Tidal Bore: A tidal phenomenon where the leading edge of an incoming tide forms a wave or series of waves in narrow, shallow rivers or estuaries.

In conclusion, the lowest tide that occurs in a half lunar month is called a Spring tide. This is when the gravitational forces of the Moon and the Sun align, causing a strong gravitational pull and resulting in a lower low tide.