Why do you think Chen and Gold can't make the same Olympic Team

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Any three senior age-eligible US Ladiea who don't need a release from another country, haven't competed for another country internationally in championships for three years before the Olympics, and are chosen by USFS can compete.
Who competes in the team event is a combination of how the disciplines are ranked internally, who wants to compete in the TE, whether they want to do both segments, USFS strong-arming, skaters' on what "prefernce" would be favored by USFS, etc.
The third US Lady given the option -- not necessarily who came in third at Nationals -- would compete in both segments if the first two US Ladies passed on what was available by the time Ladies were taken into consideration.
For the US, it looks like #1 in mens and dance will get their first pick as to whether or not they want a sub.
Pairs won't have a choice of a sub under any circumstances.
I could see the #1 in mens wanting a sub since men compete right after pairs.
But yeah, whoever the ladies skater is for the US should expect to do the whole thing.
The US has only one Pairs spot, so there wouldn't be a choice if the top Dance, Man, and Lady were to choose to do both
In Sochi, Dance and Ladies would have been top-ranked, and D/W chose to do both (as did V/M for Canada). So Ladies and Men split.
I wouldn't underestimate Shpilband or Zoueva wanting the top-ranked Dance team to do both

and deny the opportunity to number two to win a medal, so, who knows, it could be two Ladies and two Men again.