A particle is moving in the vertical plane. It is attached at one end of a string of length \[\lambda \] whose other end is fixed. The velocity at the lowest point is \[u\]. The tension in the string is \[\vec{T}\] and velocity of the particle is \[\vec{v}\] at any position. Then, which of the following quantity will remain constant.

• A.  \[\vec{T}.\vec{v}\]
• B.  kinetic energy
• C.  Gravitational potential energy
• D.  \[\vec{T}\times \vec{v}\]