premise: There are exactly six groups in this year's Civic Parade: firefighters, gymnasts, jugglers, musicians, puppeteers, and veterans. Each group marches as a unit; the groups are ordered from first, at the front of the parade, to sixth, at the back. The following conditions apply: At least two groups march behind the puppeteers but ahead of the musicians. Exactly one group marches behind the firefighters but ahead of the veterans. The gymnasts are the first, third, or fifth group. If the gymnasts march immediately ahead of the veterans, then which one of the following could be the fourth group?
hypothesis: veterans