the answer is c) the speed and direction of travel must be constant
Water and wind cause mechanical weathering and produce angular rocks, sheer canyon walls, and pebble-covered surfaces.
Well there are a couple ways.
1: The easiest, plant cells have a cell wall or extra protection. You will not find this on an animal cell, as there is only a membrane.
2: Chloroplast. This also will not be found in animal cells as they produce the plant's green color as well as the sugar.
Hope this helps!
The positive and the negative side
I hope this helps :)