Final answer:
The correct equation is D. 11 = 11² = 121, as it accurately represents squaring a number. The other options contain errors in representing the squaring operation.
Step-by-step explanation:
The correct equation that represents a mathematical truth from the given options is D. 11 = 11² = 121. This is a correct representation of exponentiation, where 11 raised to the power of 2 equals 121. The other options are incorrect because they do not accurately represent the operation of squaring a number (raising it to the power of 2). For example, option A incorrectly states that 8 equals 8 squared, which is not true as 8 squared equals 64, not 16. Similarly, option B incorrectly states that 9 equals 2 times 9, and while 2 times 9 does equal 18, this is a multiplication, not a square operation. Finally, option C is incorrect because it states that 10 equals 2 times 10, which would be 20 and not the square of 10, which is actually 100.