What is the optimal soil $pH$ for plant growth?

$A$ graph of magnetic flux $(\phi)$ versus current $(I)$ is drawn for four inductors $A, B, C, D$. Which inductor has the largest value of self-inductance?

Two trains travelling on the same track are approaching each other with equal speeds of $40\, m/s$. The drivers of the trains begin to decelerate simultaneously when they are just $2.0\, km$ apart. Assuming the decelerations to be uniform and equal,the value of the deceleration to barely avoid collision should be.........$m/s^2$.

Which of the following units represents the largest amount of energy?

$A$ $100 \ mL$ solution of $0.1 \ N$ $HCl$ was titrated with $0.2 \ N$ $NaOH$ solution. The titration was discontinued after adding $30 \ mL$ of $NaOH$ solution. The remaining titration was completed by adding $0.25 \ N$ $KOH$ solution. The volume of $KOH$ required for completing the titration is $............ \ mL$.

In an elastic collision of two particles,which of the following quantities is conserved?