Read the following passage and choose the letter A , B, C, or D to indicate the correct word or phrase that best fits each of the numbered blanks.    

  Because of mobile phones’ explosion in popularity, many schools have opposed, or even banned, their use in the classroom. Yet an increasing ___(29) ___ of educators are now turning to cell phones in order to bolster student engagement and learning. ___(30) ___ mobile-phone use should be limited to situations (31) _______ the technology genuinely enhances instruction, the advanced functionality of today's cell phones makes them ideal for 2 1st century lessons. For example, many schools use the devices to poll students in class via text message.      Some schools encourage students to use their phones Cameras to snap pictures for use as inspiration in art classes. Others allow students to capture photographs of a post-lecture whiteboard. In seconds, kids car grab a detailed image of a teacher's notes on the board and email it themselves, resulting in incredible study tool.      On field ___(32) ___, students can participate in scavenger hunts by snapping pictures of items on a teacher-supplied list. Mobile phones can also help facilitate class discussion. Teachers might ask students to run a Google Search for information on a particular topic. An alternative to presenting the information via lecture or having students read it from a textbook, discussion-integrated Web searchers are ___(33)___ more engaging, increasing the adds that students will retain the information.  (Adapted from https://www.lonelyplanet.com)

Yet an increasing ___(29) ___ of educators are now turning to cell phones in order to bolster student engagement and learning.