77. LED Circuit

Question.3

You are using a blue 5 mm LED with the following datasheet values:

VF (typical) = 3.0 V at 20 mA
VF (maximum) = 3.4 V at 20 mA

The LED is connected to a 3.3 V supply through a 150 Ω resistor.
During testing, the LED sometimes does not glow properly.
What is the most likely reason?

The resistor value is too high
The LED is defective
There is insufficient voltage headroom
Blue LEDs require at least 5 V supply
The supply voltage is too stable

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