About IoT, which among the following is not correct?

IoT sensors are broadly classified by the type of signal their raw sensing element produces. An analog sensor's underlying element outputs a continuously varying quantity (a voltage or resistance that changes smoothly over a range) that must be sampled by an analog-to-digital converter before a microcontroller can use it. A digital sensor's underlying element instead outputs a discrete state directly, most commonly a simple two-state HIGH or LOW signal, though some digital sensors produce multi-bit encoded data or include their own internal converter, so the microcontroller can read it without a separate ADC.

• Light sensor: a light-dependent resistor's resistance varies continuously and smoothly with incident light intensity, an analog output, so the statement about the light sensor holds.

• Microphone: a standard electret or dynamic microphone converts sound-pressure vibrations into a continuously varying voltage and needs a separate converter to become digital, so calling an ordinary microphone a digital sensor does not hold.

• Keyboard: each key switch reports one of exactly two states, pressed or released, a discrete HIGH or LOW signal, a digital sensor, so that statement holds.

• Push button: a mechanical switch toggling between exactly two states, open or closed, is also a discrete digital signal, so that statement holds too.

Only the microphone statement breaks this analog-digital pattern: three of the four statements correctly match their device to its natural, typically-taught signal type, while the microphone statement assigns a digital classification to a device whose standard sensing element (an electret or dynamic diaphragm) is fundamentally analog. Specialized MEMS microphones with a built-in converter are a qualified hardware exception, not the general, unqualified claim made in the statement, so under the conventional classification this question tests, the microphone statement remains the one that is not correct.