37. All animals, ______ their size, breathe once for every four heartbeats.
—Hi, this way, please.—OK. I sometimes have no sense of ________when I arrive at the crossroad.
Along with the letter was his promise ________he would visit me this coming Christmas.
I was just talking to Margaret when Jackson________.
Now many crops can be improved ________different species of plant, such as rice, wheat.
________of food ________to the countries struck by the seaquake(海啸).