Some seeds like soap nuts have very hard shell. Why is it so?

Assertion (A) : Trees are plants which are very tall. They have a hard and thick brown stem. Reason (R) : Lamina is thin, flat, broad, green part of leaf.

I originate from the digestive canal of the embryo. I am a tube like structure I have very important blood vassels that connect the embryo with the placenta. Who am I?

Do you clean your hands with soap before eating, why is it so?

Noble gases have very low boiling points. Why ?

Answer the following questions: (a) A steady current flows in a metallic conductor of non-uniform cross-section. Which of these quantities is constant along the conductor: current, current density electric field, drift speed ? (b) Is Ohm's law universally applicable for all cnducting elements ? If not, give examples of elements which do not obey Ohm's law. (c ) A low voltage suply from which one needs high currents must have very low internal resistance.Why (d) A high tension (HT) supply of say, 6kV must have a very large internal resistance, Why ?

Why do soaps not work in hard water?

Exlain why diamond is very hard.

Place a fist full of Bengal gram (or any other seeds) seeds in a bowl of water. Do you find some seeds float while others sink? Which seeds do you think will not germinate and why?