Biopsy - Histopathological studies for malignancy:
A biopsy involves taking a sample of tissue for microscopic examination to detect the presence of cancer cells. This is a correct match.
Bone marrow test - To detect leukemia:

Bone marrow tests can help diagnose leukemia by examining the marrow for abnormal cells. This is also a correct match.
MRI - Uses strong electric field and ionising radiations:

MRI (Magnetic Resonance Imaging) does not use ionizing
radiation. It uses strong magnetic fields and radio waves
to create images of organs and tissues. This makes the statement a mismatch.
Computed tomography - Uses X-rays to generate

3-D image of organs:

A CT scan (or CAT scan) uses X-rays to generate detailed 3D images of internal structures, which is a correct match.
Thus, the mismatch is , as MRI uses magnetic fields, not ionizing radiation.