Which property can be adjusted to control the number of particles emitted in Unity's Particle System?

The emission rate is the property that controls the number of particles emitted in Unity's Particle System. By adjusting this setting, you can specify how many particles are generated per second, which directly affects the density and visual richness of the particle effect in your scene. A higher emission rate results in more particles being emitted, creating a more intense effect, while a lower rate yields a sparser effect.

The other properties listed serve different functions. Speed influences how quickly the particles move and can affect how the particle effect behaves over time, but does not dictate the quantity. Lifetime determines how long each particle exists before it disappears, impacting how long the effect lasts but again, not the quantity emitted. Size affects the dimensions of individual particles, altering their appearance but not their emission frequency. Each of these properties plays a role in shaping the final look and feel of the particle effects, but the emission rate is specifically responsible for controlling the number of particles generated.