In a ΔABC, which of the given condition holds?

We know that the sum of the lengths of any two sides of a triangle is greater than the length of the third side.

So, in ΔABC,

AC + AB > BC

AC + BC > AB

AB + BC > AC

We also know that the difference between the length of any two sides of a triangle is smaller than the length of the third side.

So, in ΔABC,

AC − AB < BC

AC − BC < AB

AB − BC < AC

Hence, from the given options, AB − BC < CA is the correct alternative.