Which organs of the urinary system allow you to consciously control when urination will occur? a. kidneys and the urethra b. kidneys and the ureters c. bladder and the urethra d. bladder and the ureters

I believe the answer is C.

In order to urinate your urethral sphincters contract, these are two muscles used to control the exit of urine in the urinary bladder through the urethra.

(I concluded this through light research, this has not been in any of my health classes personally, so I could be incorrect.)

"What controls the release of urine from the bladder?

Urethral sphincters. The urethral sphincters are two muscles used to control the exit of urine in the urinary bladder through the urethra. The two muscles are either the male or female external urethral sphincter and the internal urethral sphincter."

"Does your bladder contract when you pee?

Muscles of Micturition: The Detrusor and Urethral Sphincters. Micturition, or urination, is the act of emptying the bladder. ... The detrusor muscle that surrounds the bladder contracts. The internal urethral sphincter relaxes, allowing for urine to pass out of the bladder into the urethra."

oxygen +1 most likely

cells use diffusion to get substances in and out of themselves. that diffusion will occur across the cell membrane or the outer covering of the cell. because we are talking about the surface of the cell, surface area and volume are  important factors here. as a cell increases in size, its surface area and volume increase as well.  we call that the surface area to volume ratio (sa: vol).  but the catch is that  volume increases at a greater rate than surface  area. in other words, as a cell gets bigger, the sa: vol gets smaller. so a really small cell like bacteria is mostly cell membrane (surface) with very little contents (volume). a really big cell like an egg, is mostly insides with a super thin membrane. so what ends up happening is that the cell cannot efficiently diffuse all of the stuff it needs in/out to survive. therefore cell size is limited to about 100mm. so how do we make organisms bigger than 100mm? cells divide! by dividing and becoming multicellular, organisms are able to grow!   check out the diagrams i attached to see the effect of sa: vol. i hope this ! good luck!