Which of the following is wrong regarding Searle's apparatus method in finding Young's modulus of a given wire?

• A

  Average elongation of wire will be determined with a particular load while increasing the load and decreasing the load.

• B

  Reference wire will be just taut and experimental wire will undergo for elongation.

• C

  Air bubble in the spirit level will be disturbed from the central position due to relative displacement between the wires due to elongation.

• D

  Average elongation of the wires is to be determined by increasing the load attached to both the wires.