What do $A, B, C$ and $D$ represent in the following figure?

• A

  $\mathrm{A}$ : carrier protein, $\mathrm{B}$ : symport, C: uniport, D : antiport
• Correct answer
  B

  A : carrier protein, B : uniport, C: antiport, D : symport
• C

  A : carrier protein, B : antiport, C: symport, D : uniport
• D

  A : carrier protein, B : uniport, C: symport, $\mathrm{D}$ : antiport

Hence, the correct answer is option: 'B'.