A hog breeder would use a backcross to

Options

A. determine if a particular hog is genotypically pure
B. eliminate chances of congenital malformations
C. maintain a pure line of desirable traits
D. produce a bigger and healthier strain

Explanation

### Step-by-Step Solution:

1. **Understanding Backcross**: A backcross is a breeding method where a hybrid organism (the offspring of two genetically different parents) is crossed back with one of its parents or an individual genetically similar to its parent. This method is used to reinforce certain traits in the offspring.

2. **Identifying the Purpose of Backcross**: The main purpose of performing a backcross is to maintain or enhance specific desirable traits in a population. This is particularly important in breeding programs where certain characteristics are sought after.

3. **Evaluating the Options**:
- **Option 1**: "To determine whether an organism is genotypically pure or not." This is incorrect because a test cross is used for this purpose, not a backcross.
- **Option 2**: "To eliminate the chances of congenital malformations." This is also incorrect as backcrossing does not specifically target congenital malformations.
- **Option 3**: "To maintain a pure line of the desirable traits." This is correct, as backcrossing is often used to reinforce desirable traits within a breed.
- **Option 4**: "To produce a bigger and healthier strain." This is misleading; while backcrossing can lead to healthier offspring, it is not the primary goal.

4. **Conclusion**: Based on the evaluation of the options, the correct answer is that a hog breeder would use a backcross "to maintain a pure line of the desirable traits."