Most Americans suffer from three colds every year, each lasting three to ten days. Although a lucky few never catch colds, the average American misses several days of work each year with this illness, and this means that when you sneeze the economy catches a chill, too; colds are estimated to cost our society more than $19 billion annually in lost labor. Seeking relief, we spend hundreds of millions of dollars for medicine to clear our heads and ease our pain.
( ), doctors agree, sadly, that no practical cure has yet been found for this disease, which occurs more often than all others combined.

( ) 안에 들어갈 접속사로 알맞은 것은?

1. Nevertheless
2. However