Sure, here are the completed sentences:

1. Several companies have come under **criticism** for their misleading advertising.
2. I've finally come to a **decision** about the subject for my thesis.
3. At the end of your essay, come to a **conclusion** about the causes of the problem.
4. The result came as a **surprise** to the research team.
5. Mathews came into **contact** with other geologists also gathering data.
6. Medicine has come a **long way** since the twentieth century.
7. I think I came **across** as a little nervous when I gave my presentation.
8. There are many aspects of the fuel crisis to consider, but what it all comes **down** to is the fact that the supply of oil will finally run out.
9. David has sometimes come in for **criticism** regarding the way he collects evidence.
10. The team from China and France have come **together** on this project.
11. Without formal qualifications, people in my country will come up **against** serious obstacles when they try to find a job.
12. Many elder people come **down** with flu at this time of year.
13. The small team of scientists believe they have come **up** with a solution.

Sure, here are the completed sentences:

1. Several companies have come under **criticism** for their misleading advertising.
2. I've finally come to a **decision** about the subject for my thesis.
3. At the end of your essay, come to a **conclusion** about the causes of the problem.
4. The result came as a **surprise** to the research team.
5. Mathews came into **contact** with other geologists also gathering data.
6. Medicine has come a **long way** since the twentieth century.
7. I think I came **across** as a little nervous when I gave my presentation.
8. There are many aspects of the fuel crisis to consider, but what it all comes **down** to is the fact that the supply of oil will finally run out.
9. David has sometimes come in for **criticism** regarding the way he collects evidence.
10. The team from China and France have come **together** on this project.
11. Without formal qualifications, people in my country will come up **against** serious obstacles when they try to find a job.
12. Many elder people come **down** with flu at this time of year.
13. The small team of scientists believe they have come **up** with a solution.