Question

A colony of 2^120 bacteria occupies a total volume of 1.3*10^15*m^3

Answer 1

The complete question is 
A colony of  2^120 bacteria occupies a total volume of 1.3 x 10^15 m^3. The surface area of a planet is approximately 5.42 x 10^14 m^2. 
Complete parts​ (a) and​ (b) below. 

a) Assume that the bacteria are distributed uniformly over the​ planet's surface. How deep would the bacterial layer​ be? (You can find the approximate depth by dividing the bacteria volume by the​ planet's surface​ area.) 
____m 

b) Would the bacteria be​ knee-deep, more than​ knee-deep, or less than​ knee-deep? 

A. The bacteria would be less than​ knee-deep. 
B. The bacteria would be more than​ knee-deep. 
C. The bacteria would be​ knee-deep. 
D. It depends on the height of the person

Part a) 
Find the approximate depth 
= (bacteria volume / planet surface area) 
= (1.3 x 10^15 m³) / (5.42 x 10^14 m²) 
= 2.4 m 

the answer Part a) is 
2.4 m

Part b) 
No information is given about the height of the 'people' on this planet, and hence we cannot guess at their average knee height. 
2.4 meters is about 7.9 feet. That is obviously above the knee for any human, but. again, the question does not explicitly state that we are talking about Earth and humans

therefore

the answer part b) is the option
D. It depends on the height of the person