Beta particles cannot penetrate very far into solids because they a. have low velocity b. have negligible mass c. have no mass d. are confined to orbits

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.)

causes

fossil fuels burn

cities become more industrialized

human population grows worldwide