It is synchronous because all three flip flops use the same clock and the same edge of the clock.
I do not think your truth table Q's are consistent.
First row has QA, QB snd Qc = 0, yielding the D, S, R, J and K you have listed. But the three Q's after the clock will not be 0, 0, 0.
Second row Q's should match the first row Q after the clock, and they do not.
If they did match, then your truth table says the three Qs are always zero.
I think you want to continue your truth table a few more lines.
If you do it in a spreadsheet, you can copy it down as many rows as you like.
The equations are straight forward. D = Qc prior row, S = Qa prior row, toggle = 1- prior row for JK ff if J = 1, etc
I got a repeating pattern regardless of Q at start. It just takes a different number of steps for it to settle down.
If this is studying for the test, its ok to ask the forum.
If this is an actual test, then it is inappropriate to ask the forum, you need to ask your instructor.