Question

an asynchronous binary up counter, made from a series of leading edge - triggered flip - flops, can be changed to a down counter by
taking the output on the other side of the flip - flops (instead of q)
clocking of each succeeding flip - flop from the other side (instead of q)
changing the flip - flops to trailing edge triggering
all of the mentioned

Explanation:

In an asynchronous binary up - counter made of leading edge - triggered flip - flops, when we clock each succeeding flip - flop from the $\overline{Q}$ (the other side instead of $Q$), the counting sequence is reversed and it becomes a down - counter. Taking the output from the other side of the flip - flops just gives the complement of the normal output and doesn't change the counting direction. Changing the flip - flops to trailing edge triggering doesn't change the up/down counting nature.

Answer:

Clocking of each succeeding flip - flop from the other side (instead of Q)