D. The cell is the growing and developing basis of life I cm long 6 cm long 30 cm in length )5 weeks (b)14 weeks (c)20 weeks Human fetal development. (a)At 5 weeks, limb buds, eyes, the heart, the liver and rudiments of all other organs have started to develop in the embryo, which is only about lcm long. (b)Growth and development of the offspring, now called a fetus continue during the second trimester. This fetus is 14 weeks old and about 6cm long(cThe fetus in this photograph is 20 weeks old. Now the fetus grows to about 30cm in length.D. The cell is the growing and developing basis of life Human fetal development. (a)At 5 weeks, limb buds, eyes, the heart, the liver and rudiments of all other organs have started to develop in the embryo, which is only about 1cm long. (b)Growth and development of the offspring, now called a fetus, continue during the second trimester. This fetus is 14 weeks old and about 6cm long. (c)The fetus in this photograph is 20 weeks old. Now the fetus grows to about 30cm in length