Kindly explain question numbers 26 and 27

26).

The complete pattern of a pendulum is ...

-- out to one side

-- back to the center

-- out to the OTHER side

-- back to the center.

So, on the graph, the complete period is one up-loop and one down-loop.

That's 6 seconds. (b)

27).

This question is just asking for the frequency, without using the word.

Frequency is always (1/period).  That's 1/6 of a second. (a)

(This kinda makes sense.  If you want to do something in 6 seconds, you need to do 1/6 of it every second. Right ?)

there is no correct list among the choices you've provided.

the list might look something like this:

-- baby human

-- piccolo

-- flute

-- soprano singer

-- trumpet

-- tenor singer

-- trombone

-- baritone singer

-- baritone horn

-- bass singer

-- tuba

since i had to make up the list myself, i made it easy on myself, and i didn't try to shuffle the string instruments and woodwinds into it too.