On the first day of class, Professor Bigelow tells her geography students that pop quizzes will be given at unpredictable times throughout the semester. Clearly, studying for Professor Bigelow's surprise quizzes will be reinforced on a schedule.

B. Variable Interval

Explanation:

The variable interval schedule is the schedule in which the schedule is not fixed with regard to anything that means anything can be happen at any time

there is no fixed time

Since in the question it is mentioned that the Professor Bigelow told her students that the quizzes would be provided at non-predictable times so here the surprise quizzes would be reinforced on a variable interval schedule

Therefore the correct option is b.

question - in 1827, john walker, a druggist in a small english town, tipped a splint with sulphur, chlorate of potash, and sulphid of antimony, and rubbed it on sandpaper, and it burst into flame. the druggist had discovered the first friction-chemical match, the kind we use to-day. it is called friction-chemical because it is made by mixing certain chemicals together and rubbing them. although walker's match did not require the bottle of acid, nevertheless it was not a good one. it could be lighted only by hard rubbing, and it sputtered and threw fire in all directions. in a few years, however, phosphorus was substituted on the tip for antimony, and the change worked wonders. the match could now be lighted with very little rubbing, and it was no longer necessary to have sandpaper upon which to rub it. it would ignite when rubbed on any dry surface, and there was no longer any sputtering. this was the phosphorus match, the match with which we are so familiar. according the paragraph what was the benefit of the new phosphorus match? it burst into flame when rubbed on sandpaper. it was made by mixing chemicals. it could be ignited on any dry surface. it threw fire in all directions.

answer - matches required natural chemicals