What mechanical waves needs a medium to travel through?

a. all mechanical waves need a medium to travel through
b. surface waves only
c. transverse and longitudinal waves only
d. longitudinal and surface waves only

Imagine that twenty i.u.’s of enzyme z were catalyzing the above reaction for one minute, under vmaxconditions, in a 3.00 ml assay volume. the assay is buffered with 20 mm phosphate buffer, ph 7.60. what will the ph be at the end of that one minute?