Correct Option: C

Older clear-glass Pyrex manufactured by Corning before 1998, Arc International’s Pyrex products, and Pyrex laboratory glassware is made of borosilicate glass. According to the National Institute of Standards and Technology, borosilicate Pyrex is composed of (as percentage of weight): 14% boron, 51% oxygen, 0.3% sodium, 1% aluminium, 38% silicon, and less than 1% potassium. Pyrex glass cookware manufactured by World Kitchen is made of tempered soda-lime glass instead of borosilicate. World Kitchen justified this change by stating that soda-lime glass was cheaper to produce, is the most common form of glass used in bakeware in the US, and that it also had higher mechanical strength than borosilicate— making it more resistant to breakage when dropped, which it believed to be the most common cause of breakage in glass bakeware.