The look of confusion on their faces became more and more apparent
"The look of confusion"＝「困惑している顔」
"on their faces"＝「彼らの顔に」
"became more and more apparent"＝「どんどんと顕著になっていった」
“プリントの表をなぞる学生達には困惑の表情が広がった“
→"As they handled the front side of their handouts, the students' look of confusion became more and more apparent."
アメリカ合衆国 
