Choose the correct option

1. Horses
   [invade|pass on|release|rub|signal|stick out] noses when they like each other!
2. If you
   [invade|pass on|release|rub|signal|stick out] a dog's territory, it might bite you.
3. Rabbits thump their hind legs on the ground as a warning
   [invade|pass on|release|rub|signal|stick out] when they are in danger.
4. Some insects use touch and sound to
   [invade|pass on|release|rub|signal|stick out] information to other insects.
5. Some plants
   [invade|pass on|release|rub|signal|stick out] chemicals to protect themselves from insects.
6. When snakes hiss, they
   [invade|pass on|release|rub|signal|stick out] their long tongues making a distinctive sound.