27. Transistor Application

Question.3

Refer to the attached PCB image of an LED level indicator circuit.
The components highlighted in red are small through-hole transistors, each placed next to an LED and a resistor.

What is the primary role of these transistors in this circuit?

Image Source: electronicsworkshops

To set the LED color and brightness directly
To allow low-power signals to control higher LED current
To protect the LEDs from reverse voltage
To filter noise from the LED power supply

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