Which Statement Best Describes the Relative Refractory State When the Membrane

Which statement best describes the relative refractory state when the membrane has not fully returned to its resting state?

A) The same strength of a single stimulus can create a firing threshold.
B) No amount of stimulus relative to the previous impulse will produce a firing threshold.
C) Rapid repetition of the same strength stimulus will create a firing threshold.
D) A larger stimulus than the previous stimulus can produce a firing threshold.