In Capillary Electrophoresis,hydrodynamic Sample Injection

In capillary electrophoresis,hydrodynamic sample injection:

A) involves sample injection into the capillary by applying a positive pressure to the sample inlet.
B) is best for analytes that have a higher electrophoretic mobility.
C) involves sample injection into the capillary by applying a voltage.
D) is sometimes considered to be a "biased" type of sample injection.