7. Which of the following is wrong? (A) Divide a uniform spring of spring constant k into two identical halves. The spring constant of each half is 2k. (B) Fix one endpoint of a rope on the edge of a cliff, and release the other endpoint from equal height. At the moment when the free endpoint falls a distance h below the other endpoint, its velocity v is smaller than for any h ＞ 0. (See Fig. B above.)(C) Newton'slaw is necessary for the momentum conservation of physical systems.(D) Given arbitrary 3-dimensional vectors A, B, and C, the following identity bolds: A X(BXC = B(AㆍC) - C(AㆍB)(E) The angular momentum of a point mass in linear motion at constant velocity can be non-zero.