Solution:
Book-gills (e.g., Limulus) and book-lungs (scorpion) are the respiratory organs met with in some members of the phylum Arthropoda.
Book-gills and book-lungs are the respiratory organs of some animals of the phylum
Book-gills (e.g., Limulus) and book-lungs (scorpion) are the respiratory organs met with in some members of the phylum Arthropoda.