This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Lymphatic System, Subject name: Surgery
Grade I lymphedema means: 
Select and explain. 
A. Pitting edema upto the ankle, B. Pitting edema upto the knee, C. Non - pitting edema, D. Edema disappearing after overnight rest
D: Edema disappearing after overnight rest
Answer: D: Edema disappearing after overnight rest 
Explanation: Brunner's clinical classification of Lymphedema Grade Clinical features Subclinical (latent) Excess interstitial fluid and histological abnormalities in lymphatics and lymph nodes, no clinically apparent lymphedemaQ. I Pitting edema, largely or completely disappears on elevation and bed restQ II Non - pitting edema, does not significantly reduce upon elevationQ. III Edema associated with irreversible skin changes, i.e. fibrosis papillaeQ.