A 25-year-old primipara, 34-weeks of gestation, she was admitted to the hospital for progressive edema in lower limbs for 2 weeks and severe headache for 8 hours. Her prenatal visits were normal in the first trimester. P
E: P: 75bpm, R: 20bpm, BP 170/100 mmHg, edema (+++), 24-hour urinary protein test: 3.6g, liver function: ALT and AST moderately elevated. Which of the following is the most likely diagnosis?
选项：

A:mild preeclampsia ;
B:severe preeclampsia ;
C:gestational hypertension ;
D:preeclampsia superimposed upon chronic hypertension