Mounting multiple partitions on a disk
Since you're using bash (I assume a recent version of bash), you can use some advanced features, like associative arrays and indirect variables

#!/bin/bash

# If no argument is passed, act on all partitions.
if (( $# == 0 )); then
    a=t b=t c=t
else
    for arg; do
        if [[ $arg == a|b|c ]]; then
            declare $arg=t
        else
            echo "ignoring argument '$arg'"
        fi
    done
fi

declare -A uuids=( [a]=1234 [b]=3456 [c]=5678 )

for dest in a b c; do
    if [[ ${!dest} == t ]]; then
        sudo mount /dev/sb$dest "${uuids[$dest]}"
    fi
done


Note that the [ command acts differently when given different numbers of arguments. With just a single argument (such as [ $a="t" ]), you'll get a success exit status if the argument is not empty (and the string "$a=t" is not empty no matter the value of $a). You have to put spaces between all the operators and operands for [ and test and [[.