D I think, but double check elsewhere.
No it can not because photosynthesis makes glucose and cellular respiration breaks down the glucose in to Carbon Dioxide and H2O (water).
Hope this helps!
Answer:
density = 5520 kg/m^3
Explanation:
given that
radius of earth = 6378 km
G = 6.67 x 10⁻¹¹ m³/kg.s²
g = 9.80 m/s²
we know,

mass of earth


M = 5.972 x 10²⁴ kg
density =
V = volume of the earth = 4/3πr³
V = 4/3 x 3.14 x (6378 x 10³)³
V = 1.08 x 10²¹ m³
density = 
density = 5.52 x 10³ kg/m^3
density = 5520 kg/m^3
I think the answer is a although I'm not 100% sure. I think it's becuase it's natural and nothing man made has ever intervened with it
Since they are rowing against the current, their velocity realtive to the groud is 20-1.5 = 18.5km/h
So the distance travelled is 18.5km/h*0.5h = 9.25km
Going back with the current their ground realative velocity is 20+1.5 = 21.5km/h so the time it takes them to return 9.25 km is 9.25km/(21.5km/h) = 0.43h ~= 26 min