The ACT won’t test adverbs in every section, but introductory adverbs show up often enough that you should know how to punctuate them.
Sometimes a sentence (or independent clause) begins with a word that modifies the whole idea that follows. These words often comment on the statement or set up how you should interpret it.
Basically, many sentences begin with a word that essentially modifies (or describes) a whole sentence, usually by virtue of modifying the verb.
The word “basically” is an introductory adverb. It works like a brief interruption at the start of the sentence. Because of that, you should place a comma right after it.
Here are some other words that commonly work this way. When you see one of these words at the beginning of a sentence or an independent clause, a comma should follow it:
On the ACT, the key skill is simple: if the sentence starts with one of these “setup” words, check that there’s a comma right after it.