Question

giant squid live deep in the ocean.
it is hard for scientists to find them.
because ← joining word
↺ revise your work. say giant squid before using a replacement word like them so that its clear what youre talking about.
it is hard for scientists to find them, because giant squid live deep in the ocean.

Explanation:

The original sentences need revision for clarity. First, state "Giant squid" to clarify the referent of "them". Then, structure the sentence with the joining word "because" to show the cause - effect relationship. The correct revised sentence should place the cause (Giant squid live deep in the ocean) after "because" and the effect (it is hard for scientists to find giant squid) before.

Answer:

Because giant squid live deep in the ocean, it is hard for scientists to find giant squid.