Add punctuation: In 1834 Jacobi proved that if a singlevalued function of one variable is doubly periodic then the ratio of the periods is imaginary
A: In 1834 Jacobi proved that if a single-valued function of one variable is doubly periodic then the ratio of the periods is imaginary.

Add punctuation: If you want to know in advance what turns me off Rude unpolite people
A: If you want to know in advance what turns me off: Rude, unpolite people!

Add punctuation: Most breathing problems require admittance into a hospital until the patients inability to take in sufficient oxygen has been resolved
A:
Most breathing problems require admittance into a hospital until the patient's inability to take in sufficient oxygen has been resolved.