Misc: How did nurse Edith Cavell die in 1915?

Questions

What green vegetable comes in varieties such as cos & mignonette?

What group landed in America in 1620?

What group of superheroes display the number 4 on their chests?

What gun cannot be silenced, due to all the noisy gasses which escape the cylinder gap at the rear of the barrel?

What habit forming plant did Columbus find on his first new world trip?