A student produces a sound while standing near a large wall. An echo is heard by her at time $t$ after the sound is made. The speed of sound in air is $v$. Which expression is used to calculate the distance between the student and the wall?
- A$v \times t$
- B$v \div t$
- C$(v \times t) \div 2$
- D$(v \div t) \div 2$