Plate tectonics describes Earth’s outer shell as being broken into many moving plates that float on the hotter, plastic layer beneath them called the asthenosphere. These plates drift because heat-driven convection currents in the mantle move the rock, and gravity helps pull dense oceanic plates down at subduction zones while pushing at mid-ocean ridges. This combination of forces causes the plates to collide, slide past one another, or pull apart, leading to earthquakes, volcanoes, and mountain building. The idea that the surface is a single rigid shell isn’t accurate because the continents and oceans sit on separate plates that move relative to each other. The atmosphere doesn’t drive plate movement; its processes are atmospheric and surface phenomena, far removed from the deep-Earth forces that govern plate motion. The oceans aren’t the sole driver either, though interactions at oceanic boundaries and water loading can influence patterns of movement. The fundamental drivers are mantle convection and related forces like slab pull and ridge push.

This question tests vocabulary for lowering amount or size. To reduce means to make something smaller or use fewer resources—cutting down, decreasing, or trimming where you’re using less. For example, you can reduce energy consumption by turning off lights when not needed or reduce waste by recycling more. The other options don’t fit as well: increase means to become larger or more, expand means to grow in size or scope, and intensify means to become stronger or more extreme, not simply smaller. That’s why the best choice is to reduce.

A closed conducting path that lets electric charges move is a circuit. A circuit is a complete loop that includes a power source, conductors, and a device (the load) so current can flow from the source, through the wires, through the device, and back to the source. If the loop is broken, you have an open circuit, and current cannot flow. An insulator would resist or block the flow, and an electron is simply a charged particle, not the path itself. So the term that describes a loop of material capable of transferring electricity is a circuit.

In flowering plants, the female reproductive structure is the pistil. The pistil sits at the center of the flower and is made up of the stigma, style, and ovary. The stigma is the sticky tip that catches pollen, then pollen travels down the style to the ovary where fertilization of the ovules can occur. After fertilization, the ovary often develops into fruit containing seeds. Petals attract pollinators but aren’t the reproductive part, and sepals protect the bud. The stigma is part of the pistil, but the entire female structure is the pistil, which is why it’s the correct answer.

Photosynthesis uses carbon dioxide from the air and water from the soil as the starting materials that plants convert into sugar and oxygen using light energy. In this process, carbon dioxide and water are the reactants, and oxygen and glucose are the products. The idea is that the plant takes in CO2 and H2O, powered by light, to build sugars for energy and growth, releasing oxygen in the process. The other options mix up substances that are produced (oxygen and glucose) or aren’t part of this reaction (carbon monoxide or nitrogen).