The following table gives the sales of batteries manufactured by a company over the years (numbers in thousands).



Which battery has the lowest total sales across all seven years?

Let's calculate the total sales for the given battery types across all 7 years by summing up their columns:
1. For 4AH:

$$\text{Total}=75+90+96+105+90+105+115=676$$

2. For 7AH:

$$\text{Total}=144+126+114+90+75+60+85=694$$

3. For 35AH:

$$\text{Total}=102+84+105+90+75+45+100=601$$

4. For 55AH:

$$\text{Total}=108+126+135+75+90+120+145=799$$

Comparing the total values ($676,694,601,799$), the battery type 35AH has the lowest total sales ($601\text{ thousand}$).