Answer:

Explanation:
Given that,
Heat required, Q = 1200 J
Mass of the object, m = 20 kg
The increase in temperature, 
We need to find the specific heat of the object. The heat required to raise the temperature is given by :

So, the specific heat of the object is
.
Answer:
My answer is 7.2 km
Explanation:
When Stephen goes to the south and then to the east, he is drawing a right triangle, where the 4 km and 6 km sides are the cathetus of a right triangle.
Then we use the Pithagorean theorem to solve this problem. We need to find the hypotenuse.
c² = a² + b²
c² = 4² + 6²
c² = 16 + 36
c² = 52
c = 7.2 km
Light travels faster than sound ,because sound can only travel waves.
The answer & explanation for this question is given in the attachment below.
D. all of the above
Hope this helps!