Amino Acid Entry into Cells Can Occur Via Uniporters or Symporters.If

Amino acid entry into cells can occur via uniporters or symporters.If the rate of leucine entry into the cell increases when the pH decreases,this suggests:

A) leucine is being transported by a uniporter.
B) leucine is being actively pumped across the membrane against its concentration gradient.
C) leucine is being transported by a H⁺ symporter.
D) leucine is crossing the membrane via simple diffusion.