we must find economical methods for extracting oil from shale
Related Translations:
采油动态: behavior of oil recoveryoil recovery performance
必须: must; have to; be obliged to ; necessary 短语和例子必须指出 it must be pointed out that ...; 我们必须服从命令。 we must obey orders. 你必须按时到达那里。 you must be there on time. 我们必须马上出发。 we must start at once