The associated problems with this weed include its competitiveness, difficultyofcontrol, and the reduction of quality through genetic contamination of pure lines of rapeseed and the like.
The difficulty for marketers is creating the right kind of buzz and learning to control it.
难的是那些销售人员要建立正确的商业推销手段,并且学会控制这种商业手段。
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However, efforts to control them are consistently undermined by the difficulty and expense of identifying mosquitoes-of which there are at least 3,500 species, many of them hard to tell apart.