1
GATE CSE 2007
+2
-0.6
Consider the $$CFG$$ with $$\left\{ {S,A,B} \right\}$$ as the non-terminal alphabet, $$\left\{ {a,b} \right\}$$ as the terminal alphabet, $$S$$ as the start symbol and the following set of production rules:

For the correct string of (earlier question) how many derivation trees are there?

A
$$1$$
B
$$2$$
C
$$3$$
D
$$4$$
2
GATE CSE 2007
+2
-0.6
The language $$L = \left\{ {{0^i}{{21}^i}\,|\,i \ge 0} \right\}$$ over the alphabet $$\left\{ {0,1,2} \right\}$$ is
A
Not recursive.
B
is recursive and is a deterministic $$CFL$$.
C
is a regular language.
D
is not a deterministic $$CFL$$ but a $$CFL$$.
3
GATE CSE 2007
+2
-0.6
Consider the $$CFG$$ with $$\left\{ {S,A,B} \right\}$$ as the non-terminal alphabet, $$\left\{ {a,b} \right\}$$ as the terminal alphabet, $$S$$ as the start symbol and the following set of production rules:

Which of the following strings is generated by the grammar?

A
$$aaaabb$$
B
$$aabbbb$$
C
$$aabbab$$
D
$$abbbba$$
4
GATE CSE 2006
+2
-0.6
Consider the following statements about the context-free grammar
$$G = \left\{ {S \to SS,\,S \to ab,\,S \to ba,\,S \to \varepsilon } \right\}$$
$$1.$$ $$G$$ is ambiguous
$$2.$$ $$G$$ produces all strings with equal number of $$a's$$ and $$b's$$
$$3.$$ $$G$$ can be accepted by a deterministic $$PDA$$.

Which combination below expresses all the true statements about $$G?$$

A
$$1$$ only
B
$$1$$ and $$3$$ only
C
$$2$$ and $$3$$ only
D
$$1, 2$$ and $$3$$
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