Final answer:
The investment function, government spending function, and export function are all drawn as flat lines because they do not vary with changes in income or output. These functions are determined by factors other than current income or output levels.
Step-by-step explanation:
The investment function, government spending function, and export function are all drawn as flat lines because they are assumed to be independent of a change in income or output. These functions are typically depicted as horizontal lines because they do not vary with changes in the level of economic activity.For example, the investment function represents the level of investment spending in an economy, and it is assumed to remain constant regardless of changes in income or output. This is because investment decisions are typically based on factors other than current income or output levels, such as interest rates or business expectations.Similarly, the government spending function represents the level of government spending, which is determined by government policy decisions and is typically not directly influenced by changes in income or output. Likewise, the export function represents the level of exports, which depends on factors such as exchange rates or global demand and is not directly affected by changes in domestic income or output.