When a bicycle tire gets mud on it, the tire becomes slippery. what does the mud do to the tire? a. increases the force of gravity b. increases the force of friction c. it decreases the force of friction d. it decreases the force of gravity

The answer to this is C.

Question: When a bicycle tire gets mud on it, the tire becomes slippery. What does the mud do to the tire?

C. It decreases the force of friction.

First mud is not a solid. It is more of a slow liquid like corn syrup. And when you are caught in mud or trying to ride past the mud you loose friction with the ground.
You could also resemble friction with traction. In a car. If there is water & oil mixed on the road and you go past it at a high mph range. You will loose traction and start skipping against the mixed substance. This reduces your traction (friction) with the ground.

Final

C. It decreases the force of friction

Neptune is the eighth planet from the sun. it was the first planet to get its existence predicted by  mathematical calculations  before it was actually seen through a telescope on sept. 23, 1846. irregularities in the orbit of  uranus  led french astronomer alexis bouvard to suggest that the gravitational pull from another celestial body might be responsible. german astronomer johann galle then relied on subsequent calculations to   spot neptune via telescope. previously, astronomer galileo galilei sketched the planet, but he mistook it for a star due to its slow motion. in accordance with all the other planets seen in the sky, this new world was given a name from greek and roman mythology — neptune, the roman god of the sea.

Initial velocity,  u = 4.9 m/sfinal velocity = v m/sinitial height,  h₁ =  245 m    final height, h₂ = 0a = -9.8  m/s²time taken = t secondss = ut + 0.5at²⇒  (h₂-h₁) = ut + 0.5at²⇒  0-245 = 4.9t + 0.5×(-9.8)×t²⇒ -245 = 4.9t - 4.9t²⇒ 4.9t² -4.9t -245 =0solving it, we get   t = 7.59sv  = u +  at = 4.9 -9.8×7.59 = 4.9 - 74.38 = -69.48 m/svelocity is  69.48 m/s downward