Disingenuous (adjective)

1. Not candid or sincere, typically by pretending that one knows less about something than one really does.
2. Insincere or insincerely claiming to be unaware of something.

Origin:

From the latin word "dis-" meaning away or not, and "ingenuus" meaning natural, native, and genuine.

Examples:

1. His disingenuous explanation was not believed by anyone.
2. The politician's disingenuous response was not well received.
3. Her disingenuous apology was not accepted.
4. The employee's disingenuous claim of ignorance was not accepted.
5. The student's disingenuous request for more time was denied.