Answer
The match for #5 is "a", corpora cavernosa
Work Step by Step
There are three cylinders of tissues in the penis-- the corpus spongiosum and the two corpora cavernosa. The corpus cavernosa are basically spaces that become filled with blood in response to nervous stimuli generated by sexual desire. The engorgement of the corpus cavernosa ( and the corpus spomgiosum) results in penile erection.The male urethra passes through the corpus spongiosum.