Which statement is true for electric field lines?
field lines should always be parallel to the equipotential lines.
field lines should always be perpendicular to the equipotential lines.
field lines should always be parallel to each other.
field lines should always be crossing each other.
field lines should always be perpendicular to each other.

The correct statement is

Field lines should always be perpendicular to the equipotential lines.

we know that, along equipotential lines, work done in moving a charge is zero. Since work done is zero, the force on the charge must be perpendicular to the displacement. the electric force on a charge is parallel to the direction of electric field. hence the electric field must be perpendicular to the displacement or equipotential lines.

float.

archimedes' principle

denser than water sinks in water.

denser than mercury would sink in it