Explanation:
The correct answer is E: Syphilis, gonorrhoea.

Explanation:
Both syphilis and gonorrhoea are sexually transmitted diseases caused by bacteria:

- Syphilis is caused by the bacterium *Treponema pallidum*.
- Gonorrhoea is caused by the bacterium *Neisseria gonorrhoeae*.

The other diseases listed are caused by viruses or other pathogens:
- Tuberculosis is caused by *Mycobacterium tuberculosis* (bacteria), but smallpox is caused by a virus.
- Measles is caused by a virus, as is polio.
- Sleeping sickness is caused by a protozoan (not bacteria).