The movement of carbohydrates from the leaves of the tree to the root is primarily a function of the

Translocation of organic materials in plants is explained by:

The direction of phloem sap in the phloem is ........

Based on various pieces of evidence,it is known that the downward movement of food in plants takes place through:

$A$ : The translocation in phloem is bidirectional.
$R$ : The source and sink relationship is variable.

$A$ few drops of sap were collected by cutting across a plant stem by a suitable method. The sap was tested chemically. Which one of the following test results indicates that it is phloem sap?