the past and future

choose the correct words to complete the sentences.

2.-theree scientifific advances took place during the mid- 1890s: the discoveries of x-reys, radiactivity, and the electron. (discoveries/invention/population)

3.-The population of the CD in 1983 led to the development of CD-ROMs and DVDs. (exploration/invention/population)

4.-Landing a spacecraft on Mars in 1997 was a gread achivement in space techonology (achivement/disaster/terrorist act).

5.-In 2003, a powerful earthquake struck bam, Iran. It was a disaster for people living in the area. (a disaster/an assassination /a population)

6.-No one knows why many ships and planes have disappeared in the bermuda triangle. It still a mystery ( a discovery/ an epidemmic / a mistery)