Which of the following is not equal to 46.3 meters? a. 46,300 mm b. 0.463 hm c. 4630 cm d.0.00463 km

46.3 
A. Meters need to be converted to millimetres 
 1 m = 1000 mm
  46.3 m x 1000 mm/m = 46 300 mm
therefore this is correct 

2. meters need to be converted to hectometer (hm)
100 m  = 1 hm
46.3 m x 1/100 hm/m = 0.463 hm
this is correct 

3. meters are converted to centimetres
1 m = 100 cm 
46.3 m = 46.3 m x 100 cm/m = 4630 cm
This is correct 

4.meters are converted to kilometers
1000 m = 1 km
46.3 m = 46.3 m x 1/1000 km/m = 0.0463 km 
The option given is 0.00463 km, therefore this is the incorrect option