David believes that he is president of the United States and that there is a conspiracy to kill him. David's beliefs are examples of that are considered symptoms of schizophrenia.

Delusions; positive

Explanation:

Schizophrenia is a mental health disorder in which an individual's thought pattern, behaviour and emotions are distorted. The individual often loses touch with reality. Someone having schizophrenia often witness any or a combination of the following symptoms such as hallucination, disorganized speech, impaired motor behavior, delusions.

Delusion is a positive symptom of schizophrenia, which involves the individual having an unrealistic belief that they are very important and as such some certain persons are after them to hurt them.

David's beliefs are examples of delusions that are considered positive symptoms of schizophrenia.

answer; earthquake;

muslims have taken his goods and products to different parts of asia an indonesia. sometimes just traveled and trade, but in other occasions, stayed in the place and made a living.

trade was the key for muslims economies to prosper. their commerce routes reached far places like malaysia and java in the 11th century.

another important factor for prosperity was that muslim states served as the middle point for european traders.

they used to travel by land but sailing the seas -the indian ocean- really increase the exportation of products.