Excess amounts of salts, water, and materials are expelled in the urine from the
a.
kidneys
b.
bladder
c.
urethra
d.
gallbladder

The kidneys excrete excess amounts of salts, water, and other materials in the form of urine.

Urine is stored and expelled, from the body, from the bladder thru the urethra.

Depending on what direction the question is coming from either A or B would be the correct answer.

Urine is excreted from the kidneys but expelled from the bladder. I would verify from your teacher which direction the question is going: where these substance form urine (kidneys) or where they are excreted from the body (bladder)