is the word sandwich a compound word?

Iopened the door quietly,then stood in the doorway rewrite using ..ing participle

Hi how are i have some questions about english subject can you answer for me ?

Which choice is a major detail from paragraph two? a) the great wall is a large network of several walls and towers. b) the great wall looks like a long wall snaking its way across china. c) the great wall was constructed over hundreds of years beginning in 221 b.c. d) the great wall construction encouraged several independent kingdoms to unite.