Question

squid wash up on shore.
scientists can study them.
because ← joining word
combine the sentences into one sentence. use the joining word.

Explanation:

To combine the sentences using "because", we need to show the causal relationship. The first sentence is the reason (squid washing up) and the second is the result (scientists can study them). So we structure it as "Scientists can study squid because they wash up on shore." (Note: Adjusted pronoun for clarity, original "them" refers to squid, so rephrased for better flow while keeping the meaning.)

Answer:

Scientists can study squid because they wash up on shore.