What are sexually transmitted diseases?

(a) What are sexually transmitted diseases ?
Name any one which is caused by bacteria and one caused by viral infection.
(b) Mention any two methods to avoid such diseases.

(a) Diseases that spread through the sexual contact are called sexually transmitted diseases. ,
(i)gonorrhoea or syphilis
(ii)warts, HIV, AIDS.
(b)(i) use of condoms on penis.
(ii) use covering on vagina.