13. On the Great Plains, nineteenth-century settlers used mud and grass to build their homes, doing it without timber and nails.

(A) settlers used mud and grass to build their homes, doing it without

(B) settlers, using mud and grass to build their homes, did it without

(C) settlers used mud and grass to build their homes, making them while not having

(D) settlers used mud and grass to build their homes, making do without

(E) settlers’ homes were built of mud and grass, making do without

答案是B，making do是啥意思阿？