Indoor exercises，however，are never as helpful as those taken out of doors in pure，fresh air.
Indoor exercises，however，are never as helpful as those taken out of doors in pure，fresh air.
然而，室内锻炼，决没有在有纯而新鲜的空气的室外有益。
Indoor exercises，however，are never as helpful as those taken out of doors in pure，fresh air.
然而，室内锻炼，决没有在有纯而新鲜的空气的室外有益。