Which of the following statements regarding encryption is true?

Group of answer choices

a$.$ In symmetric key encryption, a company must use a different set of keys with each trading partner.

b$.$ In public key encryption, a company must find a way to securely communicate a different public key to each trading partner.

c$.$ A certificate authority $($CA$)$ is a trusted third party that verifies a company$$s private encryption key.

d$.$ All of the above statements are true

e$.$ None of the above statements are true