Which system of equations has exactly one solution?

A. and  has one solution.

Step-by-step explanation:

for first: they meet each other at one point.

for second: they never meet each other.

for third:

infinite solutions

for fourth: they never meet each other.

54 km / hours

step-by-step explanation:

we need to convert seconds to hours

60 seconds = 1 minutes

60 minutes = 1hour

15 m         60 second   60 minutes

  * *         = 54000 meters/ hour

second     1 minute             1 hour

now we need to convert meters to km

1000 m = 1 km

54000 m       1 km

*   = 54 km / hours

hour               1000m