Perhaps the most familiar liquid-solid solution is dental amalgam, used to fill teeth when there is a cavity. Approximately 50% of the amalgam material is liquid mercury to which a powdered alloy of silver, tin, and copper is added.

“I have lost my pen” is the active voice of the above sentence.

I - subject, pen-object, lose (lost )- transitive verb.

Hence, ‘My pen has been lost’ is the passive.

The correct phrase is Yours obediently. But it is seldom used today.

At primary level, it is better to teach in mother language because it helps children in learning in natural atmosphere

3x+6y+4x=?

3x+4x+6y=7x+6y

 While changing from 'active to passive', the object 'A' becomes the 'subject' in passive voice.

The teacher behavior should be instructive.

This is to lead the understanding and learning in students in correct directions.

The Indus  is a transboundary river of Asia and a trans-Himalayan river of South and East Asia

The 'northern part of the subcontinent' consist of northwest lands which have access to Indus river and the northeastern regions have access to Ganga river.

As the northern parts consist mainly rows of hills, water formed from here is pure and sources of fresh water. These rivers have been the source of water for farmers in the northern region to cultivate crops.