Which of the following is considered a renewable resource?

Trees are considered a renewable resource because they can be replenished naturally over time through the process of growth and reproduction. When managed sustainably, forests can provide a continuous supply of timber and other forest products without depleting the resource. For instance, when trees are harvested, new trees can be planted or allowed to grow back, maintaining the ecosystem's balance.

In contrast, natural gas and coal are fossil fuels formed over millions of years from the remains of ancient organisms. They are finite resources; once extracted and consumed, they cannot be replenished within a human timeframe. Iron, while abundant and recyclable, is not a renewable resource since mining it depletes ore deposits and does not allow for natural regeneration in a sustainable manner as trees do.