What are the two most important processes in the cycling of oxygen in and out of the atmosphere?
a. weathering and erosion
b. evaporation and precipitation
c. photosynthesis and respiration
d. lightning fixation and fossil fuel emission

the total distance that martina travels that day is

(distance from home to mom's office) plus (distance from mom's office to school)

plus (distance from school to library) plus (distance from library to friend's house)

plus (distance from friend's house to martina's house).

(we don't know what any of these distance actually is.)