Concept:Use corresponding angles and the linear pair property of angles on a straight line.Explanation:Since AB∥CD, the corresponding angles are equal.Therefore, r=80∘.Angles CFE and CFG lie on the straight line EFG, so their sum is 180∘.Thus, r+5k=180∘.Substitute r=80∘:80∘+5k=180∘5k=180∘−80∘5k=100∘Divide both sides by 5:k=5100=20∘Answer:k=20∘, which is option B.