Some invertebrates in antarctica have which compound in their blood to protect against the cold

The correct answer is glycerol. This is what animals like seals have. It's basically a bunch of fat tissue that is found under the skin in large quantities to isolate the body and protect it from the immense cold. Seals aren't the only ones as there are many animals in the polar regions who have it.

Answer(a); // soil salinization and waterlogging;