39.

Answer and Explanation

Your Answer is

Correct Answer is D

Explanation

The first sentence "The architect Eero Saarinen created the design symbolizes the theme of the monument - St.Louis as 'the entrance to the West'", the second sentence "The arch bridge will have an external stainless steel and internal concrete structure" before and after the sentence It is a simple parallel relationship, no correlative words are needed, and item D is correct. Meanwhile "during this period", therefore "so", however "however", do not meet.