1. Doctors have cured many deadly diseases in recent desades.
2. In last 100 years scientists have splited the atom and discovered DNA
3. Mary hasn't mastered Spanish, but she can communicate.
4. Every twelve months, the Earth circles the Sun.
5. She does needs help right now.
6. The students have had three tests this month.
7. Paul talks to several doctors about his problem, but nobody knows why he is ill.
8. I have been studying to become a vet since 2015.
Объяснение:
1 - Present Perfect.
2 - Present Perfect.
3 - Present Perfect.
4 - Present Simple.
5 - Present Simple.
6 - Present Pefect.
7 - Present Simple.
8 - Present Perfect Continuos.
Во втором по смыслу, что они начали делать сто лет назад и к этому моменту закончили. В Present Perfect - начали когда-то делать и закончили к какому-то моменту.
Регулярно, с частотностью - Present Simple.
В последнем Present Perfect Continuos, потому что начали в , но до сих пор не закончили.
Present Perfect образуется: have/has + Ved/V3.
Present Simple образуется: V/V + s(es)
Present Perfect Continuos образуется: have/has + been + Ving
