EXPLOITATION because all three activities are based on known facts. (1) mergers is an intentional act accomplished through planned action. Companies merge or take over other firms after it has done its studies and analyses. They do not do it to exploring. They do it for gaining. (2) Acquisition, same reasoning. (3) Divestiture; here too a company or investor divest as a reaction to the current or forecast condition of the current investment or project that it will be unproductive or unprofitable. This cannot be exploring. A company would not leave (divest) a profitable project to pursue the unknown (explore); it leaves the current project (divest) because it wants to cut losses or opportunity cost. All three are exploiting. Cheers.

Definitely a well crafted strategy is assumed to be behind every Merger , Acquisition or Restructuring and thus will not be counted as a Exploration. The internal taskforce/new product development/strategy offices looking to identify such targets for M&A would be exploration as at that stage decision making can influence the final set of choices within exploration/exploitation while the acquisition is an act. 

In my opinion it can be context specific, some M&A's can be purely to exploit current firm resources (e.g. take over/merger of one firm over a supplier firm/firm which is vertically integrated in its value chain; so as to ensure constant supply of raw materials; so the objective is to exploit) there may also be cases that a firm may want to explore into a new market / technology and may acquire a firm in a host country/ firm for exploring into a new technology: this to is an exploitation because a firm may want to leverage what the target firm has.

However, there may be firms which might have just invested time and effort to merge smaller organizations and this may involve some non rational decision making or just see/explore (looking for an emergence) what can be done with smaller firms/target firm (e.g. some venture capitalists just invest in a firm without all due diligence)

This is just my thought; I may be not totally correct on this !

Mergers and Acquisitions are done because of existing financial problem, liquidity decrease .. etc, so it is an intentional activity, done by large companies after doing the proper financial analysis of the troubled company. Thus this action is EXPLOITATION as it is  based on a very well known facts. However, divestitures is an exploration activity for getting more profits , diversification creates safety for investors due to severe financial crisis.          

It is multi-dimensional. It is either exploration or exploitation depending on the circumstances that call for the process. On another note the policies that are applied if they are not closely scrutinized by the merging entities they can lead to exploitation of the other party. The issues business being a legal persona have to be taken into cognizance.