**Explanation:**

In a multiprogramming environment, more than one process resides in the memory. This means that the operating system is capable of loading multiple programs into the memory simultaneously, allowing them to execute concurrently.

Here is a detailed explanation of why option 'C' is correct:

**1. Understanding Multiprogramming:**
Multiprogramming is a technique used in operating systems to maximize the utilization of the CPU. It allows multiple processes to be loaded into memory, with the CPU switching between them to execute instructions. This enables the illusion of concurrent execution, even though the CPU can only execute one instruction at a time.

**2. Execution of Multiple Processes:**
In a multiprogramming environment, the processor executes more than one process at a time. This means that the CPU switches between different processes, allowing them to make progress simultaneously. However, it's important to note that the CPU executes instructions from one process at a time, but it switches between processes so quickly that it gives the appearance of simultaneous execution.

**3. Programs Developed by Multiple People:**
The statement in option 'b' is unrelated to a multiprogramming environment. It refers to the collaboration of multiple people in developing programs, which is a common practice in software development but not directly related to the concept of multiprogramming.

**4. Multiple Processes in Memory:**
Option 'c' is the correct answer because multiprogramming involves loading multiple processes into memory. These processes are allocated memory space and resources, allowing them to execute concurrently. The operating system manages the allocation of memory and resources to ensure efficient execution of multiple processes.

**5. Single User, Multiple Programs:**
Option 'd' is incorrect because multiprogramming allows multiple users or a single user to execute many programs at the same time. It's not limited to a single user; instead, it enables efficient execution of multiple programs, regardless of the number of users.

In conclusion, in a multiprogramming environment, more than one process resides in the memory, allowing the CPU to switch between them and execute instructions concurrently.