The following questions are based on the following grammar:

S -> AB | b

A -> aA | ?

B -> CD

C -> bA | AA

D -> AB | BC

For each question, to get credit you must check all and only the symbols that have

the stated property.

(a) Check all and only the nullable symbols.

I) S

II) A

III) B

IV) C

V) D

(b) Check all and only the variables that derive a terminal string.

I) S

II) A

III) B

IV) C

V) D

Now, modify the grammar to eliminate all productions that involve one or more symbols that do not derive a terminal string.

(c) Check all and only the variables that appear in some sentential form derived from S using this modified grammar.

I) S

II) A

III) B

IV) C

V) D

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I understand a) (A and C) and b) (S, A, and C). However, I need some help with c). Your help is much appreciated! =)