What prevents pregnancy 100% of the time?

Abstinence is the only thing that is proven to prevent pregnancy 100% of the time.

Sexual Abstinence

Sexual abstinence is a decision to not engage in any genital contact. The decision is normally made for a particular moral, religious, legal, or health purpose. It is the act of not having sex – the individual definition of which can vary from no sexual contact to everything but intercourse.

An epidemic is a large and localized outbreak of a sickness or disease.  a pandemic is a large global outbreak of a sickness or disease. 

This is a pretty on point question because all we need to do is replace 's' in the equation with '35'.the calculation will be9.95 + 0.30s = c9.95 + 0.30 (35) = c9.95 + 10.5  = cc = 20.45