1. Problem: Choose the best alternative for which activity uses digital signal. Digital signals are discrete signals used in modern communication such as the internet. Analog signals are continuous, like voice through loudspeakers. Answer: (iii) Chatting in internet uses digital signals. 2. Problem: Identify which plant belongs to the division algae. Algae are simple, non-flowering plants such as Spirogyra. Pea is a flowering plant, Moss is a bryophyte, Cycas is a gymnosperm. Answer: (iii) Spirogyra belongs to algae. 3. Problem: Which kingdoms have cell walls in their cells? Monera (bacteria), Fungi, and Plantae have cell walls. Animalia do not have cell walls. Protista is variable but usually has some cell walls. Answer: (iv) Fungi, Plantae, Monera have cell walls in their cells.