20. Based on the Prolog program below, what goal should be used to find the siblings of sue? parent (jill, sue). parent (jill, sally). parent (john, sue). parent (john, sally). sibling (x, Y)-parent (z, x), parent (z, Y). Sue and sau 21. Briefly describe the task of each of the following. A. Lexical analyzer B. Parser C. Code Generator 22. Based on the grammar below, draw a parse tree showing that the string "drip drip drip" is a Leak. Leak: 23. Show that the grammar below is ambiguous by drawing two distinct parse trees for the string "drip drip drip." Leak Leak