Answer and Explanation:
1. The heat that members of the secret annex is caused because they cannot open any windows during the day, to avoid being discovered. They can only open the window at night and it is still a small window in a place that does not provide good ventilation. In this case, as they were living in a totally closed place, we can imagine that the heat was indescribable, in addition to the stuffy feeling. However, the place was also extremely cold in winter.
2. Dussel was becoming very familiar with Mrs Van Dann. Their friendship was so close that it felt like a flirtation between them.
3. It means the beginning of the defeat of the Nazi forces. That's because on June 6, 1944, 160,000 Allied soldiers landed and occupied 80 km of the French coast to defeat Nazi troops and prevent them from advancing.
4. Anne is disappointed by Peter's laziness to educate himself, his lack of responsibility for religion and his lack of conviction about all things. This put him completely at odds with Anne and was a major cause of her disinterest.
5. Anne and the others must have felt extremely sad, hopeless and terrified, because they knew that they would live in a terrible and terrifying situation, and may not even survive, which in fact happened to most of them.