Questions 11 to 18 are based on the conversation you have just heard.

A．built-in bookshelves
B．freestanding bookcases
C．hanging bookshelves
D．glass cases

A．the brief duration of weather pattern
B．the variability of the mesoscale phenomena
C．the difficulty of measuring the ocean’s large-scale currents
D．the possible impact of mesoscale fields on weather conditions