Asked to nominate their ideal body figure

=When asked to nominate their ideal body figure

= When they were asked to nominate their ideal body figure (they 即 one in four children )

【说明】最后一种用法是时间状语从句，必须使用连词；前两种表达法是分词短语作时间状语，分词前面可以用连词，也可以不用连词。