Shofar, Sukkah and Lulav: Is There a Connection Between Shofar and Sukkah v’Lulav?

The Rambam’s Mishneh Torah is divided into fourteen books according to subjects or classes of laws. For example, the laws of Shabbos and the annual holidays that fall in different seasons and times of the year are in Sefer Zemanim, the Book of Seasons. Each book is further divided into sections of halakhos. In the case of Sefer Zemanim, those sections are Hilkhos Shabbos, Hilkhos Eruvin, Hilkhos Hamez u-Mazah, Hilkhos Shofar Sukkah v'Lulav, etc.

Why did the Rambam combine the laws of Shofar, Sukkah and Lulav into one set of halakhos?
Shofar is a mitzvah on Rosh Hashanah and ostensibly has no connection to yetzias mitzrayim. Sukkah is connected to yetzias mitzrayim and the agricultural aspect of the shalosh regalim as the chag ha’asif, the harvest festival. Lulav is perfomed on Sukkos and hence fits with Sukkos. But what is the connection between Shofar, on one hand, and Sukkah and Lulav, on the other hand?

Discussions in my Sukkah came up with the following answers:

1. There is no connection, but, the Rambam preferred to group them together rather than leave them as singletons
2. They are connected by the fact that they are mitzvos aseh, positive commandments, that occur in Tishrei
3. There are eight chapters in Hilkhos Shofar, Sukkah and Lulav corresponding to the eight days of Sukkos when Shmini Atzeres is included. The Rambam discusses the simcha shel ahava component of Shmini Atzeres in the eighth chapter of Hilkhos Shofar, Sukkah and Lulav

Rav Dovid Cohen says the connection is the celebration of success on Sukkos with Lulav on being forgiven during the y’mei ha’din of Rosh Hashanah and Yom Kippur. This is based on the Midrash Tehilllim 17.