1. The history of mammals dates back at least to Triassic time. A. Miocene and Pliocene time was marked by culmination of several groups and continued approach towards modern characters.
B. Development was retarded, however, until the sudden acceleration of evolutional change that occurred in the oldest Paleocene.
C. In the Oligocene Epoch, there was further improvement, with appearance of some new lines and extinction of others.
D. This led in Eocene time to increase in average size, larger mental capacity, and special adaptations for different modes of life.
6. The peak of the career of mammals in variety and average large size was attained in this epoch.
Rearrange the following parts to form a meaningful and grammatically correct sentence:
P. a healthy diet and regular exercise
Q. are important habits
R. that help maintain good physical and mental health
S. especially in today's busy world
Reorder the sentences into a meaningful paragraph:
1. The sun was setting behind the hills.
2. Birds were returning to their nests.
3. The sky was painted in shades of orange.
4. A cool breeze started blowing.
Rearrange the following parts to form a meaningful and grammatically correct sentence:
P. that maintaining a positive attitude
Q. even in difficult situations
R. is essential for success
S. and helps overcome obstacles effectively
For any natural number $k$, let $a_k = 3^k$. The smallest natural number $m$ for which \[ (a_1)^1 \times (a_2)^2 \times \dots \times (a_{20})^{20} \;<\; a_{21} \times a_{22} \times \dots \times a_{20+m} \] is: