IAA was first isolated from

Options

A. Corn germ oil
B. Gibberella
C. Human urine
D. Rhizopus

Answer

### Step-by-Step Text Solution:

1. **Understanding IAA**: IAA stands for Indole-3-acetic acid, which is a type of auxin, a class of plant hormones that play a crucial role in plant growth and development.

2. **Historical Context**: The isolation of IAA is significant in the study of plant hormones. It was first isolated by a scientist named Kenneth V. Thiemann.

3. **Isolation Source**: The question asks where IAA was first isolated from. According to historical records, IAA was first isolated from human urine.

4. **Confirmation of Information**: Kenneth V. Thiemann, along with Wendt, contributed to the understanding of auxins and their chemical structure in the early 20th century. This includes their work published in 1937 regarding phytohormones.

5. **Final Answer**: Based on the information, the correct answer to the question "IAA was first isolated from" is **human urine**.