Given,
Case 1: If b is positive, a & c both negative and c<a. Or
Case 2: If b is negative, both a& c positive & c>a.
Question says: are a&c in SAME DIRECTION?
Statement 1: c>a that means second case & a&c both positive.
Sufficient.
Statement 2: b is negative that means second case & a&c both positive.
Sufficient.
My answer:D
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DECODING THE MAIN QUESTION:is |c - a| = |c| - |a|?
In my opinion,
Such type of ABSOLUTE VALUE question (mentioned in main question) ask u a simple thing I.e.
the two variables are in same directions or not.TWO TYPES of SUCH QUESTION:(i)
{|c|+|a|} is either EQUAL or GREATER than {|c+a|}. When the two numbers (c & a) are in SAME DIRECTION (both positive or both negatives or both zero), both expressions [(|c|+|a|) & |c+a|] are EQUAL.
When the two numbers (c & a) are in OPPOSITE DIRECTION (one positive and another one negative), (|c|+|a|) is GREATER than |c+a|.
(ii) {|c|-|a|} is either EQUAL or LESS than {|c-a|}. When the two numbers (c & a) are in SAME DIRECTION (both positive or both negatives or both zero) & c has greater ABSOLUTE value, both expressions [(|c|-|a|) & |c-a|] are EQUAL. When the two numbers (c & a) are in OPPOSITE DIRECTION (one positive and another one negative), (|c|-|a|) is LESS than |c-a|.