Crayfish and silverfish belong to the phylum Arthropoda. Arthropoda is a large and diverse phylum of invertebrate animals that includes insects, spiders, crustaceans (such as crayfish), and other similar organisms.

Arthropods are characterized by having a segmented body, jointed limbs, and an exoskeleton made of chitin. This exoskeleton provides support and protection for their bodies. The limbs of arthropods are arranged in pairs, and they have specialized appendages for various functions, such as walking, feeding, and reproduction.

Crayfish are crustaceans and are known for their jointed appendages and hard exoskeleton. They are typically found in freshwater habitats and are an important part of aquatic food webs.

Silverfish, on the other hand, are wingless insects that are often found in damp places, such as basements and bathrooms. They also have a segmented body and jointed appendages, characteristic of arthropods.

Therefore, the correct answer is option 1: Arthropoda.