Which two words MUST contract (combine into one word) when they are next to each other? * de + el de + la a + la a + los

The two words that must contract when they are next to each other are:

1. "de" + "el" = "del"
2. "a" + "los" = "alos" (Note: This contraction is less common and not widely accepted. The correct contraction for "a los" is "a los")