I teach introductory biology classes; the students in these classes are typically new to the discipline at the college level and often find the amount and level of material challenging to absorb and retain. However, many students are nervous about asking or answering the questions I ask. Typically it's only a few of the well-prepared students who respond to the comprehension questions I pose. The less-prepared students keep their heads down. But students need to interact in class for me to determine the level at which they are understanding the material or struggling with it. Cold-calling feels threatening to many students and makes them even less likely to engage. I use an in-class review strategy to overcome this situation.