How to remove specific special characters in R

I have some sentences like this one. ``` c = "In Acid-base reaction (page[4]), why does it create water and not H+?" ``` I want to remove all special characters except for '?&+-/ I know that if I want to remove all special characters, I can simply use ``` gsub("[[:punct:]]", "", c) "In Acidbase reaction page4 why does it create water and not H" ``` However, some special characters such as + - ? are also removed, which I intend to keep. I tried to create a string of special characters that I can use in some code like this ``` gsub("[special_string]", "", c) ``` The best I can do is to come up with this ``` cat("!\"#$%()*,.:;<=>@[\\]^_`{|}~.") ``` However, the following code just won't work ``` gsub("[cat("!\"#$%()*,.:;<=>@[\\]^_`{|}~.")]", "", c) ``` What should I do to remove special characters, except for a few that I want to keep? Thanks