Two Events Occur on the X Axis Separated in Time $\Delta$

Multiple Choice

Two events occur on the x axis separated in time by $\Delta$ t and in space by $\Delta$ x.A reference frame, traveling at less than the speed of light, in which the two events occur at the same time:

A) exists no matter what the values of $\Delta$ x and $\Delta$ t
B) exists only if $\Delta$ x/ $\Delta$ t < c
C) exists only if $\Delta$ x/ $\Delta$ t > c
D) exists only if $\Delta$ x/ $\Delta$ t = c
E) does not exist under any condition