B. Economics is regarded as a science because it uses scientific method to explain human behaviour.

Here are the answers to your questions:

1. B. Economics is regarded as a science because it uses scientific method to explain human behaviour. Economics employs systematic observation, model building, and hypothesis testing, which are core components of the scientific method, to understand and predict human economic behavior.

2. C. The item that cannot be described as land is Roads. In economics, "land" refers to all natural resources, including forests, minerals like diamonds and crude oil, and the physical space itself. Roads are man-made structures and are considered capital.

3. C. An outward shift of the production possibility curve shows that economic growth has taken place. An outward shift of the Production Possibility Curve (PPC) indicates an increase in an economy's productive capacity, meaning it can produce more of both goods than before. This increase in potential output is defined as economic growth.