What is the correct plural form for the word dictionary?

The plural of dictionary is dictionaries.

Explanation:

If the word ends in y then when made plural you add ies and remove the y on most occasions.

the causes of the dust bowls were severe droughts,   lands became dry and hard, temperature was higher than usual, hot and dry conditions killed crops, high winds. because of those factors, the winds kicked up dry soil and created clouds of dust.

that would be the steamboat because none of the other things are forms of transportation