Jeffrey promised to sell Margo a Siamese kitten for $$800$ but backed out of the deal. Margo sued Jeffrey in state court for breach of contract and asked for a jury to hear the case. During jury selection, one juror, Lana, said that she did not think she could be fair to Margo because Margo did not appear to be a cat lover. Margo's lawyer asked that Lana not hear the case on the basis that she could not be fair, and the judge excused Lana. Margo also decided that another juror, Karen, looked at her in a hostile manner so$,$ without a reason given, Margo's lawyer asked the judge to excuse that juror from serving. The judge did so$.$

What is the challenge Margo's lawyer made to Karen called?