Which of the following is heavily doped?

$A$ Zener diode having breakdown voltage $V_z = 6 \, V$ is used in a voltage regulator circuit as shown in the figure. The minimum current required to pass through the Zener to act as a voltage regulator is $10 \, mA$ and the maximum allowed current through the Zener is $40 \, mA$. The maximum value of $R_s$ for the Zener to act as a voltage regulator is (in $\Omega$)

$A$ Zener diode with a power rating of $1 \, W$ is to be used as a voltage regulator. If the Zener diode has a breakdown voltage of $5 \, V$ and it has to regulate an input voltage that fluctuates between $3 \, V$ and $7 \, V$,what should be the value of the series resistance $R_s$ for safe operation? (See figure)

In the given circuit,the value of $I_{L}$ (in $mA$) will be: (in $.5$)

$A$ Zener diode is made by

In a Zener diode,