资料题：The word“serious”in paragraph 3 most probably means（　）。

In sports the sexes are separate.Women and men do not nun or swim in the same races.Women are less strong than men.That at least is what people say.Women are called“the weaker sex" , or, if men want to please them,“the fair sex" .But boys and girls are taught together at schools and universities.There are women who are famous prime ministers, scientists and writers.And women live longer than men.A European woman can expect to live until the age of74, a man only until he is 68.Are woman's bodies really weaker?The fastest men can run a mile under four minutes.The best women need 4.5 minutes.Women 's times are always slower than men 's, but some facts are a surprise.Some of the fastest women swimmers today are teenage girls.One of them swam 400 metre s in 4 minutes 21.2 seconds when she was 16.The first fastest man swimmer was an Olympic winner, named Johnny Weissmuller.His 400 metre s was 4 minutes 59.1 seconds, which is 37.9 seconds slower than a girl 50 years later! This does not mean that women are catching u with men.Conditions are very different now, and sport is much more serious.it is 80 serious that some women athletes are given hormone injections.At the Olympics a doctor has to check whether the women athletes are really women or not.It seems sad that sports have such problems.Life can be very complicated when there are two separate sexes!