Answer:
The speaker in this excerpt is Anne.
Step-by-step explanation:
Anne Frank refers to Mr. Kraler, a business partner of her father (Mr. Frank), who helped her family by providing them a hiding place and keeping them safe from Nazis.
At that time, people used to think that ulcers were caused by stress, so Anne Frank uses this excerpt as a metaphor to explain how hard and stressful it was for Mr. Kraler to help her family (the Franks) and other people hide in the annex.