trees help keep the air clean help后可以直接跟keep吗

trees help keep the air clean help后可以直接跟keep吗 help,air,trees,the,keep,clean连词成句句号 help keep the environment clean意思 Friends of the Earth help keep the environment clean.“ keep Trees can help ______ the air to keep it ______. [ &nbs Trees Keep the air clean.这句话的意思 planting tree can help( )the air clean 是用keep 的什么时态? HELP KEEP THIS AREA CLEAN. Trees can help _____ the air in the city.A to clean B clean Friends of the Earth help keep the environment clean.对“ keep help!help!KEEP FIT! Trees help to k___ the air clean.其中k___能添什么单词?