Looking for a gf pls answer

Which of these is most responsible for differences between the twentieth century to the twenty-first century?

All of these are true about using adhesive except: a. dissimilar materials can be joined. b. mixing tips are product and material specific. c. a specific application gun may be required. d. two-part adhesives are dispensed using two mixing tips

According to the video what are some tasks petroleum engineers perform check all that apply