The liquid level in limbs ABC forms ______ shape. Fill in the blank.
A U-tube filled with a liquid of volumetric coefficient of 10−5/∘C lies in a vertical plane. The height of liquid column in the left vertical limb is 100cm. The liquid in the left vertical limb is maintained at a temperature =0∘C while the liquid in the right limb is maintained at a temperature =100∘C. The difference in levels in the two limbs in mm is :