Final answer:
The word 'overreact' from the sentence contains the suffix '-act', which is added to the root word 'over' to modify its meaning.
Step-by-step explanation:
The word from the sentence that contains a suffix is 'overreact'. Suffixes are groups of letters added to the end of a word to change its meaning or turn it into a different word form, such as from a verb to a noun. The suffix in 'overreact' is '-act', making the root word 'over'. This is different from options A, B, and C ('friend', 'dizziness', and 'unsteady', respectively), as 'friend' has no suffix, 'dizziness' contains the suffix '-ness', and 'unsteady' contains the prefix 'un-'. In this instance, 'overreact' is the best example of a word using a suffix.