A．The resources of the sea are unlimited.
B．There are threats to animals and birds.
C．Sea resources have to be protected.
D．We must love fish.

A．A regular study program is essential to learning another language.
B．Eating eggs and toast is important for learning another language.
C．Learning another language is as easy as eating eggs and toast.
D．A language-learning program should be set upon eggs and toast.

A．She failed to understand the contents of the new book by Dr. Charles Adams.
B．She failed to speak Spanish proficiently after four years of study in high school.
C．She failed to finish an academic term paper about Spanish learning in high school.
D．She failed to pass the proficiency test of Spanish though she worked hard in high school.