There are 15 girls because 12 x 3 = 36 and 5 x 3 = 15
Answer: The correct option is D: Is alloyed with carbon and chromium to make stainless steel.
Explanation: Because of its physical characteristics, iron is a material that tends to oxidize easily. With the chromium alloy stainless steel is created, which for its quality can be used in the manufacture of structural steels.

can be simplified to by adding the 7 and 10 to get

.

cannot be simplified any more by combining like terms.
By distributing the 2b into the parentheses, you can simplify the expression:

Here you can just add:

Thus, the only expression that cannot simplify any more using adding like terms is the second,

.