Exercise 1:

1. Drive,

2. Dig,

3. Carry,

4. Fortify,

5. Find.

Exercise 2:

1. We're running [...]

2. I'm studying [...]

3. They're teaching [...]

4. I'm digging [...]

5. She's driving [...]

Exercise 3:

1. She teaches science.

2. They're carrying a piano.

3. I'm digging at the Roman theater.

4. She drives a train.