Wehaveknownforalongtimethatflowersofdifferentplantsopen...
问题详情：Wehaveknownforalongtimethatflowersofdifferentplantsopenandcloseatdifferenttimeofday.Thisissofamiliarthatthereseemstobenoneedtoaskthereasonforit.Yetnoonereallyunderstandswhyflowersopenandclosel...