Why the surface of shoes tyres of truck and car are made rough​

The tyres of the vehicles are usually made rough and corrugated. This is mainly done to increase the friction between the road and the tyre. The rougher the tyre is the grip between the tyre and the road is better. This consequently increases the friction which tends smooth vehicular motion.

the level of progesterone is low at the pre-ovulatory phase of the cycle but it gradually increases and the levels are high at the luteal phase. if pregnancy occurs, the level of progesterone will be high throughout the pregnancy.

if egg is fertilized and the mother gets pregnant, progesterone starts preparing the uterus for the implantation. it starts building up the lining of uterus and make it hostile of the period of pregnancy.