Perfect fifth because you are going from do to so which is 5 steps apart :) so do to ti would be a perfect seventh since theyre seven steps apart. a perfect octave would be do to do.
I believe that the instrument Shakira brought back into the mainstream with her hit Whenever, Wherever are the panpipes.
That instrument is a type of a flute consisting of numerous pipes which produce sound when blown into. The name comes from Greek mythology, where the Greek god Pan is often depicted using that instrument. Other than the panpipes, she also used the charango, which is a type of a lute.
6.
You can tell what key it is in by the starting note. Therefore, for example the first question is on "D", and it had a flat accidental. Therefore it is a Db (D flat). Now, we can use the circle of fifths
[first attachment]
to help find out where the sharps and flats fall, and since this is a major scale, the pattern is Wholestep Wholestep Halfstep Wholestep Wholestep Wholestep Halfstep (WWHWWWH).
Therefore the pattern is Dflat Eflat F Gflat Aflat Bflat C and Dflat again. You can write there as notes on the scale
[second attachment]
You can do this for the rest of question 6.
∆∆∆
7.
Just choose a key signature from the circle of fifths (an easy one is G) and put that key signature on your staff. Secondly, choose a time signature. The easiest is 4/4. If you're in "G", start in key of "G" and make a simple tune. e.g
[third attachment, scroll right]
for the other tunes, just choose different time signatures and key signatures and switch up the tune.
Hope I helped and good luck!