Questions 29 to 32 are based on the passage you have just heard.

A．Because nobody knew his address.
B．Because nobody knew his age.
C．Because Penury’s private life was a secret.
D．Because Penury was still a bachelor at the age of forty-five.

A．leaving the lignin will decrease his paper yield
B．leaving the lignin will make more paper from a tree
C．lignin is very useful in the process
D．lignin is essential for making paper