What does the term “base material” refer to with respect to masonry fasteners?

I believe the answer is: concrete, brick or block.

To put it simply, base material refers to the ingredients/substance that is used to build the structure of the fasteners. Different type of base materials would affect how strong the masonry fasteners would be and how difficult the fasteners to be used.

answer'; i believe the correct answer is (15,000) workers a year are treated for injuries caused by jacks, lifts or jack stands;