please read pages 133-136 and 140-150, and please complete the following sets of exercises. The associated pages of instruction and the exercise instructions get more mechanical/technical than I prefer to get with grammatical instruction, but these are issues I am seeing in your essays, so I figured it is worth having you check these things out and work with them a little bit.
EXERCISE S1-1 on page 136 (This is in Section S1-c.)
EXERCISE S3-1 on page 143 (This is in Section S3-d.)
EXERCISE S3-6 on page 146 (This is in Section S3-e.)
EXERCISE S4-1 on page 147 (This is in Section S4-a.)
EXERCISE S4-3 on page 148 (This is in Section S4-b.)
EXERCISE S4-6 on page 151 (This is in Section S4-5.)