Consider the following grammar and the semantic actions to support the inherited type declaration attributes. Let $X_1, X_2, X_3, X_4, X_5$, and $X_6$ be the placeholders for the nonterminals $\mathrm{D}, \mathrm{T}, \mathrm{L}$ or $\mathrm{L}_1$ in the following table :

Production rule	Semantic action
D → T L	X1.type = X2.type
T → int	T.type = int
T → float	T.type = float
L → L1, id	X3.type = X4.type addType(id.entry, X5.type)
L → id	addType(id.entry, X6.type)

Which one of the following are the appropriate choices for $X_1, X_2, X_3$ and $X_4$ ?

Consider the following Syntax Directed Translation Scheme $$(SDTS),$$ with non-terminals $$\left\{ {S,A} \right\}$$ and terminals $$\left\{ {A,B} \right\}.$$
$$S \to aA$$ $$\,\,\,\,\,$${ print $$1$$ }
$$S \to a$$ $$\,\,\,\,$$$$\,\,\,\,\,$${ print $$2$$ }
$$A \to Sb$$ $$\,\,\,\,\,$${ print $$3$$ }

Using the above $$SDTS,$$ the output printed by a bottom-up parser, for the input $$aab$$ is:

Consider the basic block given below.

a = b + c 
c = a + d 
d = b + c 
e = d - b 
a = e + b

The minimum number of nodes and edges present in the DAG representation of the above basic block respectively are

The program below uses six temporary variables a, b, c, d, e, f.

a = 1 
b = 10 
c = 20 
d = a + b 
e = c + d 
f = c + e 
b = c + e 
e = b + f 
d = 5 + e 
return d + f

Assuming that all operations take their operands from registers, what is the minimum number of registers needed to execute this program without spilling?