The shells are so hard and they are virtually (DESTROY)_______

16. The shells are so hard and they are virtually (DESTROY)_______.
17. We should arrive two days early in order to (CLIMATE)________.
18. These changes are likely to (POOR)________ single-parent families
      even further.
19. I’m afraid the hospital is desperately (STAFF)______ at the moment.
20. This book will challenge your (CONCEPT)_______ about rural life.