For a transistor in the active region:
$(a)$ Base,emitter,and collector regions should have similar size and doping concentrations.
$(b)$ The base region must be very thin and lightly doped.
$(c)$ The emitter-base junction is forward-biased and the base-collector junction is reverse-biased.
$(d)$ Both the emitter-base junction and the base-collector junction are forward-biased.
Which one of the following pairs of statements is correct?

• A
  $(a), (b)$
• B
  $(b), (c)$
• C
  $(c), (d)$
• D
  $(d), (a)$