We need to complete the sentence by filling up the blank space and we are given with two choices, either we choose "won't" or "wo'nt". This problem is a matter of English knowledge and we know that there is no such word as wo'nt so we will not choose this. Therefore, the correct answer is the option "won't" which can be also written as will not, it just the same won't and will not. To complete the sentence, we have it below:
Native plants are kept in check by surrounding community of plants and animals, so the native plants won't be invasive.
