In an attempt to guarantee the security of its innovative water purification method, the company required each employee to sign a confidentiality agreement prohibiting that its water purification ... companies using an analogous purification process.

a. prohibiting that its water purification methods be disclosed to companies
b. prohibiting them from the disclosing of its water purification methods to any company
c. prohibiting disclosure of its water purification methods to any company
d. that would prohibit them from disclosure of its water purification methods to companies
e. that would prohibit its water purification methods to be disclosed to a company

OA is c. Help?