2. Choose the best answers 1. A spon used to open the lid of a can is...
(1) first class lever
(ii) second class lever
(ii) thin class lever
(i) none of them.

2. Which simple machine is used to right the screw with screw driver?
(1) Lever (ii) Wheel and Axle (ii) inclined plane (iv) Wedge

3.Which category of the simple machine is autotly Kito
(i) Lever (ii) Wheel and Axle (iii) Pulley (iv Wedged.

4. Which type of the simple machine is the axe!
(1) Lever (2) Screw (3) Wedge (4) Inclined plane

5. Which type of the simple machine is winding road in hilly
(i) Lever (ii) Wedge (iii) Serew (iv) Inclined plane​

4 ans is 3,5ans is iv i know only this much

- calcium has greater affinity to bond with electron receptors than hydrogen does and hence, it has the ability to replace hydrogen in most of its compounds.

- lithium has 2 valence electrons in the product because it can make only 1 bond with hydrogen. beryllium has 4 valence electrons in the product because it can only make 2 bonds. it has fewer electrons than neon and can react with electron donors. each hydrogen has 2 valence electrons, the same as helium.

- the covalent bond formed between carbon and hydrogen is polar because carbon is more electronegative than hydrogen and it attracts the bonded electron pair closer to itself, thus giving hydrogen a partial positive charge.

- a hydrogen bond is a relatively weak bond that hydrogen atoms make with the electronegative atoms nitrogen, oxygen or fluorine.

so the best choice is a.) 2 calcium (ca) atoms

try answer.com that works for me