What type of system is best used to observe conservation of mass because all of the mass stays in one place? a balanced system
a sideways system
a closed system
an open system

the entire statement is true and correct.  

there's no diagram, nothing is illustrated, and no question is asked.

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.)

i think its d if wrong im sorry