Answer:
Due to early flowering in the mustard plant.
Step-by-step explanation:
The scientists discovered that the flowering time of the field mustard had changed by observing more mustard plants which produces earlier flowers. The behaviour of the mustard plant change due to the change that occur in the environmental conditions that leads to early flowering in mustard plant. If this early flowering occurs for more generation, then the mustard plant will adopt this type of behaviour in normal environmental conditions that experience by the mustard plant.