What is the product of $300\times 100$?

The correct option is (C).

We can do the multiplication of $300\times 100$ using the steps given below. 

Step 1: Multiply $0$ by each digit of $300$

Step 2: Place a zero on ones place below the product obtained above.

Step 3: Now, multiply $0$ by each digit of $300$

Step 4: Then again place two zeros on ones place below the product obtained above. 

Step 5: Now, multiply $1$ by each digit of $300$

Step 6: Add the three products to obtain the final answer.

Therefore, the product of $300\times 100$ is $30000$.