11. Whenever we are in ______ trouble, we should never lose______ heart.
A. a; the B. a; a C. /; / D. /; the
12. Some scientists think there are _______ 2，000 million flashes of lightning per year.
A. in short B. on average C. as usual D. in total
13 _______, people injured in the earthquake are _______.
A. Generally; picking up B. Sadly; picking up
C. Luckily; setting up D. Fortunately; picking up
