What does the word formidable in the passage mean?

Dogs make wonderful pets because they us stay happy and healthy. the topic sentence is "dogs make wonderful pets." , is this correct? i keep doubting myself.

Use the drop-down menu to choose the best verb form to complete each sentence. if he a warmer jacket, he would not have gotten frostbite. i wish that those snakes fake. if they to go to the party, they would need a ride.

How does this excerpt develop the central idea that espionage during the civil war was often carried out by untrained citizens? it enhances the reader’s understanding by explaining why training was unnecessary. it changes the reader’s perception of what information a spy was able to obtain. it explains an ordinary person’s motivation for conducting espionage against the enemy. it adds moral complexity to espionage, due to the use of secret and dangerous methods.