Jillian is mapping her co-worker's reasoning process. She puts a few words in brackets. What do the braces signify about the words they enclose?.

Which statements are true for invasive species? 1. they always stabilize an ecosystem. 2. they’re always successful in adjusting to a new habitat. 3. they often compete with the native species for resources. 4. they have the ability to displace the native species. 5. they’re always pests.