1.How mush ..... this dress cost?
A. Is
B. Does
C. Do
2.It ..... often rain in summer
A. Isn't
B. Doesn't
C. Don't
3. ....... you like swimming?
A. Do
B. Does
C. Are
4. Everybody in our family ....(help)Mummy about the house.
A. Help
B. Helps
C. Helpes

1B (в вопросе есть глагол cost, поэтому нужен вспомогат. глагол does)

2B (rain - глагол, в отрицат. предложениях с Present Simple нужен вспом. глагол does+not)

3A

4B (everybody - ед. число, поэтому helps)