In a direct mapping cache, the main purpose of comparators is to determine whether a requested memory address is present in the cache or not. Comparators are used to compare the tag bits of the requested address with the tag bits of each cache block.

In a direct mapping cache, there is a one-to-one mapping between main memory blocks and cache blocks. Each main memory block is mapped to a specific cache block based on the address. The tag bits of the requested address are used to identify the corresponding cache block.

To explain the answer in detail, let's break it down into the following sections:

1. Understanding Direct Mapping Cache:
- In a direct mapping cache, each main memory block is mapped to a specific cache block.
- The cache is divided into sets, and each set contains one cache block.
- Each cache block consists of a tag field and a data field.

2. Role of Comparators:
- Comparators are used to compare the tag bits of the requested memory address with the tag bits of each cache block in a set.
- The tag bits of the requested address are extracted and compared with the tag bits of the cache block.
- If there is a match, it means the requested memory address is present in the cache.

3. Number of Comparators in a Direct Mapping Cache:
- In a direct mapping cache, each set contains only one cache block.
- Therefore, there is only one comparator required per set.
- Since there is only one set in a direct mapping cache, there is only one comparator present in the cache.

So, the correct answer to the question is option 'C' - 1 comparator.