The C zone is called the quality control zone of the pregnancy test, if the red line does not appear in this area of the stick, it means that the pregnancy test is no longer valid, so as long as there is no quality problem with the stick, there will be a deep red line in this zone. There are control line and test line on the pregnancy test stick, C means control line and T means test line. After use, if there is no red line in the T zone and a red line in the C zone, the test is negative, indicating that there is no pregnancy. If there are two red lines in both the C and T zones of the pregnancy test, it means that the concentration of chorionic gonadotropin in the urine has increased, indicating pregnancy. However, it should be noted that the appearance of the red line in the T-zone is mainly related to the concentration of HCG in the urine, which will show a red line only after the concentration of HCG in the urine reaches a certain level. Therefore, if the menopause is short, the test is too early, just a few days after intercourse, the test will easily show a negative result due to the low concentration of HCG in the urine at that time. In women who normally have normal periods, HCG may be detected in the urine after 3-7 days of delayed menstruation, while in women with long menstrual cycles or abnormal ovulation, it may not be detected until 40-44 days after menopause. Therefore, if you want to confirm whether you are pregnant or not, it is better to go to the hospital to have your blood HCG checked more accurately and to pay attention to regular rechecking to determine the pregnancy outcome by the change of blood values.