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is/ a/ lesson/ this / only/ a few/ only /can/ it/ students/ outdoor/ activities. (Rearrange)
    A.This is a difficult lessson, so only a only few students can understand it.
    B.This is a difficult lessson, so only a few students can it understand .
   C.This is a lessson difficult , only so a few students can understand it.
   D.This is a difficult lessson, so only a few students can understand it.
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