用“ how” 改下列句子为感叹句
1.they are beautiful flowers.（用“ how” 改为感叹句）
2.it is heavy rain.（用“ how” 改为感叹句）
3.this is a big classroom.(用“ how” 改为感叹句)
4.it is very warm today.(用“ how” 改为感叹句)