The controlled experiments are performed by the scientists, when they want to study the changes in the sample on changing a single variable. So, the correct answer is option (b).
In case, all variables are kept same, no changes would be observed in the experiment sample. A controlled experiment can be performed on living thing as well as non living. But, controlled experiment cannot be performed on the things which are influenced by a lot of variables, as they cannot create realistic results. So, the option (a), (c), and (d) are incorrect.
Answer: the need of evolution
Explanation: Charles Darwin saw the differences between the birds beaks in the Galapagos island. The beaks were different because of the different food that the environment provides.
its B. Organ b/c the plants root are part of the plant
Air that resists vertical movement is said to be stable. The vertical movement of air is referred to as convection, while advection involves the horizontal movement of air and heat energy transference, Temperature differences at the Erath's surface occur wherever there are differences in surfaces substances.
It can be concluded that the energy needed for production must be less than the amount of energy produced.
