Sure! Here are the completed sentences with the correct tenses:

**III. Complete each sentence with the correct tense of the verb in parentheses.**
1. My dad should avoid (eat) **eating** salty and sugar because they (be) **are** not good for his health.
2. Do you mind (not touch) **not touching** the exhibits in the museum?
3. If I (not touch) **don't touch** all needed ingredients, I can’t make nice spaghetti.
4. I (never visit) **have never visited** the National Museum before.

**IV. Read the passage and fill in each gap with a suitable word from the list.**
The Underground is a great way to travel for both tourists and locals. It is the oldest underground metro network in the world and a few parts of this system have been operating (1) **since** 1863. The London Underground carries more than a billion (2) **passengers** every year and it spreads across 270 stations. It usually operates from 5:00 in the morning till midnight, but some lines offer 24-hour service. It is the most (3) **efficient** way to get around London. If you are a tourist, it is better to avoid the rush hours on weekdays as it gets very busy and crowded with London (4) **commuters**. These rush hours are generally between 7:30 a.m. to 9:30 a.m. in the morning, and from 5:00 p.m. to 7:00 p.m. in the evening. Also, the Underground is the (5) **cheapest** travel option from Heathrow Airport to Central London.