**Explanation:**

A condition in a contract refers to a term or provision that is crucial and central to the main purpose of the contract. It is a fundamental term that goes to the root of the contract and forms the basis of the agreement between the parties involved. The correct answer to this question is option 'B', which states that a condition is essential to the main purpose of the contract. Let's explore this further:

**Essential to the main purpose of the contract:**
- A condition is a term that is considered vital and necessary for the contract to be valid and enforceable.
- It is a requirement that must be fulfilled in order for the contract to be completed and for the parties to have their obligations met.
- Failure to comply with a condition may result in the contract being breached or terminated, and the innocent party may seek remedies or damages for the breach.

**Not essential to the main purpose of the contract:**
- A term that is not essential to the main purpose of the contract is known as a warranty.
- While a warranty is still a part of the contract and carries legal significance, its breach does not typically allow the innocent party to terminate the contract or seek damages for the breach.
- Instead, the innocent party may be entitled to claim damages for any loss or harm suffered as a result of the breach.

**Stipulation collateral to the main purpose of the contract:**
- A stipulation collateral to the main purpose of the contract refers to a term that is subsidiary or incidental to the main purpose of the contract.
- It may be a secondary obligation or promise that is not directly related to the main purpose of the contract, but still carries legal significance.
- Breach of a stipulation collateral to the main purpose of the contract may entitle the innocent party to claim damages, but it does not typically allow for termination of the contract.

In conclusion, a condition in a contract is essential to the main purpose of the contract. It is a fundamental term that must be fulfilled for the contract to be valid and enforceable. Failure to comply with a condition may result in a breach of contract and the innocent party may seek remedies or damages for the breach.