Here are the best choices for each question based on the underlined parts and context:

1. I want to buy a printer but I'm afraid it's bulky.
- **B. inconvenient** (bulky implies it's not easy to handle)

2. It's more economical to buy this car than that jet ski.
- **A. cost-effective** (economical means cost-effective)

3. You should store your data on Dropbox in case your computer collapses.
- **A. breaks down** (collapses in this context means breaks down)

4. This technology has some drawbacks that need improving.
- **B. disadvantages** (drawbacks means disadvantages)

5. The Ig Nobel prize is awarded to good-for-nothing inventions.
- **A. useless** (good-for-nothing means useless)

6. This device imitates the movements of the mockingbirds.
- **C. mimics** (imitates means mimics)

If you need further clarification on any of these choices, feel free to ask!