Was his average speed incorrectly declared to be 299 miles per hour or 289 miles per hour?请解释一下declared to be,我不懂这个to be是怎么回事,是本来就declare to do 还是什么词组,如果直接declared 299 miles可以吗,把to be

Campbell was disappointed to learn that his average speed had been 299 miles per hour.句子成分 改错It is ture that the average man often uses in his own vocabulary that was once technical. average average average average AVERAGE When the nurse took his temperature ,it was two degrees above====为什么用normal而不用average或者ordinary? However,a few days later,he was told that a mistake had been made.His average speed had been 301 miles per hour.为什么不用过去式?was made、 was 301 miles per hour? 翻译：His work at school is well above the average His average speed had been 301 miles per hour.句子成分 英语翻译Those who had watched Obama's acceptance speech as the Democrats' presidential candidate performed just as well,on average,as the white subjects.After his election victory,this was true of all the black participants. 英文数学题Ben cycles to a city at average speed X and returns at average speed Y.His average speedfor the whole trip is ( ) off的用法the average Taiwanese was three times better off than the average Paraguayuan这里off是什么意思?什么用法? 在该句子里that of是什么意义?句子是什么样的语法结构?读时看到下面一段话In stature he was above the average height; his eyes were gray,his features regular and strong; his carriage that of perfect,robust health influenced b his car was GRAHAM WALKED TO SCHOOL AT AN AVERAGE SPEED OF 3 MILES AN HOUR AND JOGGED BACK ALONG THE SAME ROUTE AT 5 MILES AN HOUR.IF HIS TOTAL TRAVELLING TIME WAS 1 HOUR,what was the total number of miles in the round tripA,3 B,3+1/8 C,3+3/4 D,4 E,5 His income is well below the average .well 请详细说一说全局话.