Which of the following expressions is true?
A. 4^3x4^4=4^12
B. 5^2x5^3>5^5
C. 3^2x3^5+3^10
D. 5^2x5^4<5^8
B. 5^2x5^3>5^5
When multiplying powers with the same base, you add the exponents. So in option A, 4^3x4^4=4^(3+4)=4^7, which is not equal to 4^12.
In option B, 5^2x5^3=5^(2+3)=5^5. This is greater than 5^5 (since they're equal), so the expression is true.
Option C is incomplete and doesn't make sense.
In option D, 5^2x5^4=5^(2+4)=5^6, which is less than 5^8. Therefore, the expression is false.