What would happen if the bicuspid valve did not exist

If the bicuspid valve did not exist or does not close completely, blood can flow backwards into the heart. This is regurgitation, also called aortic valve insufficiency. The heart then must pump that same blood out again, causing strain on the heart's lower left chamber, the left ventricle.

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.

one person pulls 90n one way and the other has 100n pulling the other way.

so the net force = 90 - 100 = -10n,

or the ans can be 10n if the picture shows -90n and 100n instead.