221. There are 5 ________ in the passage about nanometer(纳米) technology we have just read. Please tell me the general meaning of the first one.
. “ Look at him! He behaved ________ nothing had happened”, said Mary.
. They were singing and dancing to ________ their high spirits though it was very cold.
. The weather is so ________ this year that we can hardly stand so many cold days!
. The place ________ the bridge is supposed to be built should be________the cross-river traffic is the heaviest.
. I have just come in to see if I can be _________ any assistance to them.