Q2.10

The grammar whose productions are $\langle\text{stmt}\rangle \to\text{ if id then } \langle\text{stmt}\rangle$ $\langle\text{stmt}\rangle\to\text{ if id then } \langle\text{stmt}\rangle\text{ else } \langle\text{stmt}\rangle$ $\langle\text{stmt}\rangle \to\text{ id }:=\text{ id}$ is ambiguous because (a) the sentence if a then if b then c:= d has more than two parse trees (b) the left most and right most derivations of the sentence if a then if b then c:= d give rise to different parse trees (c) the sentence if a then if b then c:= d else c:= f has more than two parse trees (d) the sentence if a then if b then c:= d else c:= f has two parse trees