Answer:
oxygen
Explanation:
cells use to produce energy during cellular respiration
Implantation is the major sign of pregnancy for various women, it is a stage in which a zygote of fertilized egg limplants into the wall of the uterus.
Implantation usually takes place 6 to 10 days post ovulation, or day 20 to 24 of a menstrual cycle. However, it can take place a few days later or earlier. Once fertilization takes place, the egg remains the fallopian tuve for three days prior of getting inside the uterus and starts to implant itself to the walls of the uterus.
The heart’s electrical system is responsible for making and conducting signals that trigger the heart to beat. These signals cause the heart’s muscle to contract. With each contraction, blood is pumped throughout the body. This happens 24/7 without us having to monitor it all the time so that our heart does not stop.
