51.

Answer and Explanation

Your Answer is

Correct Answer is B

Explanation

The first sentence of the previous paragraph "We became builders in the bushes, and built our castle on the edge of the apple orchard", the first sentence of this paragraph "We will build outside the apple orchard", and the preceding and following paragraphs should be "occasionally "Relationship. Item B is correct.

Item A: Meanwhile, the two actions before and after "at the same time" cannot occur at the same time.

Item C: once and for all "once and for all", does not conform to the logical relationship between paragraphs.

Item D: at the same time "simultaneously", does not conform to the logical relationship between paragraphs.