What formula can be used to calculate [h30+]?

a. [h3o+] = log(oh-)
b. [h3o+] = 1 x 10 [-oh-]
c. [h3o+] = antilog(–ph)
d. [h3o+] = [h3o+][ oh-]

I think the correct answer is option C. The formula that can be used to determine the concentration of hydronium ions, [H3O+],  would be [H3O+] = antilog(–pH). This is from the expression of pH which is a measure that is used for the acidity of a certain solution based on the hydronium ion concentration in the solution. It is expressed as pH = -log [H3O+]. Manipulating the equation so that [H3O+] is left on one side would lead us to the same expression as given in option C.

pH = -log [H3O+]
-pH = log [H3O+]
10^-pH = 10^log [H3O+]
10^-pH = [H3O+]

where 10^x is the same as antilog of x.

[H3O+] = antilog (-pH)

The correct answer is d