You can just team them in vCenter, it will give you a total bandwidth of 40Gbps on that vSwitch but each VM vNIC will have a maximum bandwidth of 10Gbps as theyre only able to use 1 physical lync at a time. Some reading i would recommend
Youre unable to "Bond" the links into 1 logical link as far as i am aware
I have a 4 x 10 gigabit ethernet card. can I use them like 40 gb on a virtual switch.
As I said, you need to clarify what you're asking. You cannot just "glue" them all together and get a larger pipe. Please state your requirements.
No, LACP/Etherchannel basically just load balance across links. If you're downloading a single file from one server to another, you will only ever get 10Gbps. You could theoretically have a situation where you have one server simultaneously downloading a file from 4 different servers in which case the receiving server would appear to be getting 40Gbps when its really just 4x10Gbps. Depends on the load balancing algorithm you use though...