How does the magnitude of the lever arm will change if you decrease the angle?

it decreases.
it stays the same.
it increases.

It decreases.

Explanation:

Lever arm is defined as the "perpendicular distance that exists from the rotation axis to the line of action of the force". Being its magnitude related to the application of the force that produces a torque.  

To understand it better:  

The lever arm is an effective distance to apply a force with respect to a certain point, and this distance serves as an effective applied force amplification factor.

In this sense, Torque is defined as:

Where:

is the distance from the applied force to the fulcrum

is the applied force

is the angle between and

It is important to note, is maximum when . Then, assuming and remains the same, if decreases decreases, as well.

Hence:

If the angle decreases, the magnitude of the lever arm will decrease.

So, the greater the lever arm, the greater the torque and the lesser the force we have to apply.

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.