Multiple alleles can be found only when population studies are made.

Answer

**Step-by-Step Solution:**

1. **Understanding Multiple Alleles**:
- Multiple alleles refer to the presence of more than two alleles for a particular gene within a population. Unlike simple Mendelian inheritance, where only two alleles (dominant and recessive) are considered, multiple alleles introduce more genetic variation.

2. **Examples of Multiple Alleles**:
- A classic example of multiple alleles in humans is the ABO blood group system. In this system, there are three alleles:
- IA (which produces type A blood),
- IB (which produces type B blood), and
- i (which produces type O blood).
- The combinations of these alleles can result in four possible blood types: A (IAIA or IAi), B (IBIB or IBi), AB (IAIB), and O (ii).

3. **Population Studies**:
- The statement claims that multiple alleles can only be found when population studies are made. This is true because the existence of multiple alleles can only be observed when examining a group of individuals, rather than in a single individual.
- In a population, the frequency of different alleles can be analyzed, and the interactions between these alleles can be observed in terms of dominance and phenotypic expression.

4. **Conclusion**:
- Therefore, the statement is true. Multiple alleles are best studied and understood through population genetics, where the variations and frequencies of these alleles can be observed.