Explanation:

To find the necessary part of the word "Swimming," we need to determine what is essential for the activity of swimming.

Swimming:
Swimming is a physical activity that involves moving through water by using the limbs. It is a popular recreational activity and a competitive sport.

Identifying the necessary part:
To engage in swimming, certain elements are essential. Let's analyze the options given and determine which one is necessary for swimming.

Options:
a) Pool
b) Bathing suit
c) Water
d) Life jacket

Pool:
While a pool is often used for swimming, it is not a necessary part of swimming. People can swim in natural bodies of water such as lakes, rivers, or the ocean.

Bathing suit:
A bathing suit is commonly worn while swimming, but it is not a necessary part. Swimming can be done without wearing a bathing suit, such as when swimming in private pools or during certain activities like synchronized swimming.

Water:
Water is the essential element required for swimming. Without water, there would be no activity of swimming. Whether it is a pool, lake, river, or ocean, water is necessary for the act of swimming.

Life jacket:
A life jacket is a flotation device designed to keep a person afloat in water. While it is important for safety purposes, it is not a necessary part of swimming. Life jackets are typically used in situations where swimming skills are limited or for water activities that may require additional safety measures.

Conclusion:
Out of the given options, the necessary part of the word "Swimming" is Water. Water is the fundamental element required for the activity of swimming.