Went
My grandparents WENT for a walk in the park
The type of sentence given is a compound sentence. It is a compound sentence because it consists of two independent sentences: "I already said yes to someone else" and "I can't go to the dance with you". In order to link the two sentences, the conjunction "because" is used.
Observing nature is great because you can learn so much about the world around you.
Obseving the earth can help you make new discoveries
The real meaning of euphemism friendly fire is term in military bases means accidentally attacking your own military unit hope this helps :)