B (equal area 4×8= 10×m)∴m=4.8.

C

a=6 b=8？ (Pythagorean theorem? 3、4、5∶c = 10？ ∴6、8、 10)

13 or 1 19

Pythagorean Theorem 3,4,5? At the same time, it is also a right triangle when magnified k times.