what is SIT (Systems Integration Testing)?

SIT is after the unit test. In unit test every programmer tests their code alone. After that module test (unit). All modules should be integrated. While integrating those modules, v shd test the whole system. This testing process is called the Integration, In this integration test v don't find any logical or syntax errors. bcoz those errors r cleared in the unit test. here v can find only the dependency error and linking error.

search in google, u can get more details abt this...

The System Integration Testing is a testing process that shakes down source code developed and fixes any variance before proceeding to the next testing phase. To complete (or exit) SIT, there must be fewer variances than can be tolerated.

The system integration process mainly depends on (a) a formal methodology that leads to an efficient integration testing plan, and (b) a consistency checking mechanism that validates the module subsystem interfaces and intermodule interactions during all the changes of the integration testing process.

->It tests the interactions between different systems and may be done after system testing.

->It verifies the proper execution of software components and proper interfacing between components within the solution.

->The objective of SIT Testing is to validate that all software module dependencies are functionally correct and that data integrity is maintained between separate modules for the entire solution.

->As testing for dependencies between different components is a primary function of SIT Testing, this area is often most subject to Regression Testing.

http://www.softwaretesting-certification.com/

Answer no. 2 is good.