Course comparison

BBA stands for Bachelor of Business Administration and BCA stands for Bachelor of Computer Applications. Both the courses are graduate level courses. The duration of both the courses is 3 years. BCA course is technical oriented wherein a variety of computer-related subjects or technical subjects that the candidate is going to study and thereby he is going to have a good number of job opportunities in various IT companies soon after the completion of BCA course. BBA involves a variety of subjects which are related to business and management oriented. These people can have job opportunities in all the business sectors. If you join BCA then go for MCA course later. In contrast to this, if you join BBA then go for MBA course and try for job opportunities on the basis of post-graduation as the highest level of academic qualification. .

It depends on your interest and effort you put into a field. Maybe mechanics is little harder for some because you may not 'be good' at all the disciplines (programming is totally different than, say, Material Science), but you're not learning everything to an advanced level, so it's not that bad. Other courses are also pretty widespread, they just focus on things related to the main theme (f. e. Mechanical Engineering courses involve technology, welding, material Science, bearings knowledge and so on), whereas mechatronics have more distinct disciplines (brief survey of the mentioned ones, electronics, a bit of programming, etc).
Civil Engineering
It is a specialised branch of engineering that deals specifically with infrastructure. This includes the design, construction and maintenance of the physical structures including roads, bridges, buildings, dams and canals. Civil engineering is the second the oldest engineering category and is many times broken down into several sub-categories including, but not limited to, architectural, environmental, forensic, water resources, offshore and construction. Civil engineering occurs in the public sector and is found in municipalities as well as national governments. It is also found in the private sector where homeowners and large companies seek them out for their expertise.
Your interest matters.