State the main function of the following:

(i) Cerebrospinal fluid acts like a cushion and protects the brain from shocks.

(ii) Eustachian tube equalises the pressure on either side of the ear drum.

(iii) Suspensory ligament holds the lens in position.

(iv) Sperm duct serves to transport sperm from the epididymis to urethra.

(v) Lenticels facilitate transpiration in older stems.