A *sentential form* is the start symbol $S$ of a grammar or any string in $(V \cup T)*$ that can be derived from $S$.

Consider the linear grammar

$(\{S, B\}, \{a, b\}, S, \{S \rightarrow aS, S \rightarrow B, B \rightarrow bB, B \rightarrow \lambda \})$.

A derivation using this grammar might look like this:

$S \Rightarrow aS \Rightarrow aB \Rightarrow abB \Rightarrow abbB \Rightarrow abb$

Each of $\{S, aS, aB, abB, abbB, abb\}$ is a sentential form.

Because this grammar is linear, each sentential form has at most one variable. Hence there is never any choice about which variable to expand next.

Here, in *option D *the sentential forms are same but generated differently coz we are using here Bottom Up production.

**Handle:**

for example the grammar is:

$$\begin{align*} E &\rightarrow E+n\\ E &\rightarrow E*n\\ E &\rightarrow n \end{align*}$$

then say to derive string $n+n*n$:

these are three different handles shown in $3$ different colors = $\left\{ n, E+n, E*n \right \}$

that's what **option D** says