45.

Answer and Explanation

Your Answer is

Correct Answer is A

Explanation

There are two complete sentences before and after the underlined part. The previous sentence "These bidders added $170,000 to the funds of the Sanitary commission", and the second sentence "Gridley's flour sack won $275,000 within twelve months", the preceding and following sentences have no causal relationship, or similar relationship, so separate them with periods On, A is correct.