The following crossword puzzle will be used to define and solve a constraint satisfaction problem $($CSP$).$

The following words need to be placed in the crossword puzzle $($above$)$:

$$ ADS

$$ AN

$$ AT

$$ BOX

$$ BUS

$$ ON

$$ OX

$$ RAIN

$$ SASH

$$ SAT

$$ SIT

$$ SORE

Words are to be placed at $1$ down, $1$ across, $2$ down, $3$ across.

Not all words need to be used $($there is place for $4$ words only$).$

Each word may be used at most once in the crossword.

Question $52$

Not yet answered

Marked out of $2\mathrm{.}00$

Flag question

Question text

If the variables for the CSP is defined as:

X$=\{$a$1,$a$3,$d$1,$d$2\}$

what does the content of the set represent?

Select one or more:

a$1$

corresponds to $1-$across

a$3$

$$ corresponds to $3-$across

d$1$

$$ corresponds to $1-$down

d$2$

corresponds to $2-$down

a$1$

corresponds to $1-$across

a$2$

$$ corresponds to $2-$across

d$1$

$$ corresponds to $1-$down

d$2$

corresponds to $2-$down

a$1$

and a$3$

are placeholders for the first and third letters used across all words

d$1$

and d$3$

are the domain sizes for the words placed vertically

a$1$

is the first letter of every word used in the puzzle

a$3$

is the last letter of every word used in the puzzle

d$1$

refers to the number of words that can fit horizontally

d$2$

refers to the number of words that can fit vertically

a$1$

and a$3$

as actions for determining crossword intersections

d$1$

and d$2$

as difficulty levels for the words placed in the puzzle