Oil paint in tubes eliminated .
a. paint recipes
b. mineral mixing
c. pig's bladders
d. all of the above are correct

All of the above, But I'm Not sure about the Pigs Bladders.

If the measure is suppose to have six beats and we need 1 note and 1 rest, we can either do a whole note with a half note rest after that since a whole note equals 4 beats and a half note rest equals 2 beats or we could do a whole note rest with a half note after that since a whole note rest is 4 beats and a half note is 2 beats