13.One can't learn a foreign language well __________ he studies hard.

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13.Onecan''tlearnaforeignlanguagewell__________hestudieshard.13.Onecan''tlearnaforeignlanguagewell____

13.One can't learn a foreign language well __________ he studies hard.
13.One can't learn a foreign language well __________ he studies hard.

13.One can't learn a foreign language well __________ he studies hard.
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