Circuit Design

Dears 

Anyone has experince to design the  circuit consists of four inputs are a temperature sensor, a motion sensor, a sound detector, and a carbon dioxide sensor. When these sensors are detected the output signals of it will be as input to microcontroller. The microcontroller read all inputs signals and determine three outputs, are SMS should be send, window should be open and the buzzer should be triggered. When the buzzer is active automatically open the windows with the help of  DC motors acting as a switch, at the same time microcontroller gives a command to the GSM modem to send SMS to the respective person.

Your support is highly apprecited

Have answered most of this in the other posts.
It is possible that something like an Arduino board would get you going on this project, there is a lot of hardware that plugs into them, and enough different processors are supported that you will find one with the I/O capability and speed that you need.
They are used widely, and there is plenty of forum help.
You are not restricted to the Arduino IDE and C if you feel inclined to go in another direction with programming them.
There are plenty of GSM modems about that have a standard serial protocol to drive them.
Cheers,
Richard