Given this CSS what would it do?

1: h1 .header {color:blue;}

1. Give all page headers blue font.
2. Give all page headers a blue background.
3. Give all h1 tags with the class of header a blue font.
4. Give the h1 tag with the header ID a blue font.
5. Give all h1 tags a blue background.
6. Give all h1 tags blue font.

2: img[alt *=puppy] { opacity:50%; }

1. Give all images an opacity of 50%.
2. Give all images of puppies an opacity of 50%.
3. Give all images with puppy in the beginning of their alt tag only an opacity of 50%.
4. Give all images with puppy in their alt tag an opacity of 50%.

3: p::before {content: hello;}

1. Add the string hello in front of all paragraphs.
2. Add hello class to all paragraphs.
3. Add hello to the elements before every paragraph tag.
4. This is not valid CSS it would not do anything.