Why does the blending of many different diciplines present both challenges and opportunities to enviromental scientist?

The earth's inner core is the earth's innermost part. it is primarily a solid ball with a radius of about 1,220 km (760 miles), which is about 70% of the moon's radius.[1][2] it is composed of an iron–nickel alloy and some light elements. the temperature at the inner core's surface is approximately 5,700 k (5,430 °c), which is about the temperature at the surface of the sun. 

the correct answer is:

b. substitution property.

if the circle m is with inscribed ∠kjl and congruent radii jm and ml then m = ∠mjl = (kl) because of the substitution property.