Questions

Oil from Gnetum spp a gymnosperm belonging to the family Gnetaceae is used to relieve the effects of rheumatism

The lianas and shrubs of Gnetum are found in the rain forests of the western ghats.

Rolling friction or rolling drag is the force resisting the motion when a body rolls on a surface. It is mainly caused by non-elastic effects, that is, not all the energy needed for deformation of the wheel, roadbed, etc... is recovered when the pressure is removed.

Another cause of rolling resistance lies in the slippage between the wheel and the surface, which dissipates energy.

Light amplification by stimulated emission of radiation.

In each row, 

Sum of 1st two digit number + last two digit number = Middle two digit number

i.e., 1st row 15 + 40 = 55

2nd row 46 + 47 = 93

Similarly, 7x + 16 = 87 => x = 1.