How to concatenate strings obtained from a .txt document with BASH script?

I have a txt document that contains a series of arguments that I want to pass to a script. Each argument is on a separate line. I want to make a BASH script that can concatenate these arguments (with white space between each one) and then execute the script with these concatenated arguments. This is the document (d.txt) content:

-format fastq

-in data/test_data.1.fq.gz

-in2 data/test_data.2.fq.gz

-reference hg19

-alignment

-variantcalling

-annotation

-iobio

-out outdir/

-BED

I have tried to do it in the following way but it gives me an error. Instead of concatenating the s

trings, it interprets them as commands. does anybody know how I can fix it?

`

#!/bin/bash

while IFS= read -r line
do
  
  $var=$var$line
  echo $var

done < d.txt

`
This is the error I get:

./script.sh: line 6: =-format: order not found

./script.sh: line 6: =-in:order not found

./script.sh: line 6: =-in2: order not found

./script.sh: line 6: =-reference: order not found

./script.sh: line 6: =-alignment: order not found

./script.sh: line 6: =-variantcalling: order not found

./script.sh: line 6: =-annotation: order not found

./script.sh: line 6: =-iobio: order not found

./script.sh: line 6: =-out: order not found

./script.sh: line 6: =-BED: order not found

>Solution :

There is only a little mistake in assigning the Variable.

var=$var$line

instead of

$var=$var$line