Q. Which type of plants are very tall and have hard and thick brown stem?
Answer: Trees
Notes: The plants, which have hard and thick brown stem and are very tall are called trees. The stems have branches in upper part and much above the ground. For example, mango, neem. Trees are not a taxonomic group but include a variety of plant species that have independently evolved a woody trunk and branches as a way to tower above other plants for sunlight.