Please help me I am having trouble please help

5,600 x 10^3 = a) 560 b) 5,000,600 c) 5,600,000 d) 56,000

You are standing next to a really big circular lake. you want to measure the diameter of the lake, but you don't want to have to swim across with a measuring tape! you decide to walk around the perimeter of the lake and measure its circumference, and find that it's 400\pi\text{ m}400? m. what is the diameter dd of the lake?

Which term applies to agb and dge? a. obtuse b. supplementary c. complementary d. vertical